Recently jumped from my stable and boring (in a good way) RME UCX to the UAD Platform.
 
To sum it up, it's been a bumpy ride. 
 
Got a Silverface FW Unit working via Firewire pretty nicely.
Same unit w/ Thunderbolt add on was a trainwreck.
Currently trying a Twin MKii via Thunderbolt. Much better, but still dropout prone.
(Especially instantiating VST instruments such as Addictive Drums, Addictive Keys and others; auditioning patches also brings on dropouts; some just while doing basic things).
 
Here's the kicker: UA support seems to be pointing the finger at SONAR/CW. They say Sonar's efficiency at a code level is not as robust as others. Sadly, I have to admit that Presonus Studio One Pro 3.5 is on my system and plays much better with the Apollo hardware.
 
So my long winded question:
Do others have Apollo hardware working well with SONAR/CW or do you find the pairing to be "finicky"? Are you running FW, USB or TB?
 
(obviously system specs/config play a huge role here: Quick version: New i7-8700, Asrock H370 Pro4 with TB Add In Card on MB)
 
Jim Roseberry has already been kind enough to weigh in on this and I'm leaning toward paying for his consultation time to give a look at my system to see what I may have missed (his expertise is substantial and well worth the $).
 
Any past experience from the user base in general would also be greatly appreciated!

I'd say look at the add on card. Back in the old days, Presonus units use to not work with certain Firewire chipsets. I think I've read something similar happening with Thunderbolt chips.

Hope that helps.

BenMMusTech
I'd say look at the add on card. Back in the old days, Presonus units use to not work with certain Firewire chipsets. I think I've read something similar happening with Thunderbolt chips.

Thanks..and yes I'm definitely eyeing that card. 
 
Prevailing logic is "use the TB card designated for your motherboard only".
So I'm using an Asrock card approved for my Asrock MB....but I can't be sure it's not a wonky card :)

I switched to UAD Apollo Twin USB from my Roland Octapture (which always gave me grief).
I have never been happier! It did take a little adjusting but I find it extremely stable. If I ever do get a crash, the reboot of the Apollo is far simpler than the previous arrangement and doesn't need the whole system rebooted.  
Hope that helps. 

dcmg
Recently jumped from my stable and boring (in a good way) RME UCX to the UAD Platform.
 
To sum it up, it's been a bumpy ride. 
 
Got a Silverface FW Unit working via Firewire pretty nicely.
Same unit w/ Thunderbolt add on was a trainwreck.
Currently trying a Twin MKii via Thunderbolt. Much better, but still dropout prone.
(Especially instantiating VST instruments such as Addictive Drums, Addictive Keys and others; auditioning patches also brings on dropouts; some just while doing basic things).
 
Here's the kicker: UA support seems to be pointing the finger at SONAR/CW. They say Sonar's efficiency at a code level is not as robust as others. Sadly, I have to admit that Presonus Studio One Pro 3.5 is on my system and plays much better with the Apollo hardware.
 
So my long winded question:
Do others have Apollo hardware working well with SONAR/CW or do you find the pairing to be "finicky"? Are you running FW, USB or TB?
 
(obviously system specs/config play a huge role here: Quick version: New i7-8700, Asrock H370 Pro4 with TB Add In Card on MB)
 
Jim Roseberry has already been kind enough to weigh in on this and I'm leaning toward paying for his consultation time to give a look at my system to see what I may have missed (his expertise is substantial and well worth the $).
 
Any past experience from the user base in general would also be greatly appreciated!

Well, RME is the best! But to answer you question, no I have never used the Apollo.
I currently use the FireFace UFX Plus, and I can bet my life on it. 

Like Pastacrow I'm using the UAD Apollo Twin USB and find it very stable using ASIO drivers. I did experience issues trying to run with other drivers in Sonar. I moved from a Motu 24io and the Apollo is by far the most stable setup I've had. Running some big projects including multiple VST effects (UAD and native) and instruments with no issues. 

I've been running an Apollo Twin Duo USB with my Win 10 Pro x64/i7 DAW rig for several years now without any issues. Very stable ASIO performance with a variety of x64 DAW apps (SPLAT, CbB, REAPER, Studio One, etc.). I also have a Satellite Octo and (2) UAD-2 PCIe cards for a (15) DSP farm using the Apollo Twin as my main audio I/O. I have not needed to reach out to UA or any forums for UAD related support, it just works. I suspect the OP's issue is more to do with having/maintaining a stable TB connection (TB card?) than with the Apollo TB drivers. If the TB connection is flaky it will adversely affect Apollo TB performance.

Billy Buck I've been running an Apollo Twin Duo USB with my Win 10 Pro x64/i7 DAW rig for several years now without any issues. Very stable ASIO performance with a variety of x64 DAW apps (SPLAT, CbB, REAPER, Studio One, etc.). I also have a Satellite Octo and (2) UAD-2 PCIe cards for a (15) DSP farm using the Apollo Twin as my main audio I/O. I have not needed to reach out to UA or any forums for UAD related support, it just works. I suspect the OP's issue is more to do with having/maintaining a stable TB connection (TB card?) than with the Apollo TB drivers. If the TB connection is flaky it will adversely affect Apollo TB performance. 

 
I'm leaning same direction. This system is an 8th Gen Intel with a fairly new Asrock board, so I'm a bit on the bleeding edge here. There are reports of other Asrock Thunderbolt motherboards being stable but not *this one* as it's too new. May have just drawn the unlucky card of a questionable Thunderbolt functionality on this board.
 
Seems like users are having good luck with Apollo via USB. Picked one up on Reverb last weekend so I can compare stability. If it's a lot better, I may give up the Thunderbolt battle for another day and go with what works.
 
I appreciate all the input.

I use an Apollo Twin USB for my office computer and a PreSonus Studio 192 for my main music computer. No problems with either one.
 
The only way I would use Thunderbolt at the moment is with a Mac, but even then, there are TB1/2/3 compatibility issues. Many, but not all, can be solved by adapters. 

Anderton
I use an Apollo Twin USB for my office computer and a PreSonus Studio 192 for my main music computer. No problems with either one. 
The only way I would use Thunderbolt at the moment is with a Mac, but even then, there are TB1/2/3 compatibility issues. Many, but not all, can be solved by adapters. 

It does seem like the Windows/Twin USB side of things is working well for many users. I still find it curious that Thunderbolt *on my system* works fine within Studio One Pro but not in Cakewalk. I wish I had an explanation for that, but perhaps I should just use the USB Twin version and move on! :)