Hey BobF -
Any additional reports???   I'm also curious what type of controller or mixer are you using with the Tascam US16X08????

A quick (I hope) overview of how I use this.  Prior to getting the 16x08, I used a Delta66 (4x4 analog) and a mixer.  The mixer fed the Delta so I could have levels set for different pieces of gear without having to recable and reset levels when devices were changed.
 
The 16x08 has enabled me to remove the mixer from the chain.  *Today* I have inputs feeding the 16x08 as follows:
 
(16x08 mic IN1-4 +48 phantom ON)
IRT Studio spkr out -> Red Box 5 -> 16x08 IN1
AT2035 cond mic -> 16x08 IN2
 
(16x08 mic IN5-8 +48 phantom OFF)
IRT Studio direct out (no emulation) -> 16x08 IN5
Direct Box -> 16x08 IN6
Dynamic mics -> 16x08 IN7-8
 
16x08 IN9-10, line or inst
 
(Line INs)
GT-001 -> 16x08 IN11/12
THR10 -> 16x08 IN13/14
 
Outputs 1/2 and 3/4 are connected to two different input pairs on a Samson C-Control.
 
16x08 OUT1/2 are the output of the internal mixer.  These allows direct monitoring of any inputs, combined with DAW outputs.  The Tascam Settings app gives control of the internal 16x08 mixer.

 
16x08 OUT3/4 are the computer outputs.  These allow monitoring of DAW outputs.

 
Having the outputs set this way allows switching between direct and DAW monitoring with pushbuttons on the C-Control.
 
Having additional outputs allows me to reamp to any physical amp I have, feeding the amp output back thru whatever input makes sense, whether I'm using a non-emulated direct out from the IRT Studio (to feed a spker/cab sim), the Red Box 5 being fed by the IRT Studio, a Bugera V22 or the Blackstar HT5RH, or the Blackstar's own direct output. 
 
There are lotsa ways to use this thing.  I use more inputs to keep from moving cables around more than I need simultaneous recording capability.  The preamps are sweet, with plenty of overhead for high level transients.  It has a good mix of input types (for me).
 
If there is one thing I don't like, it's getting used to having the mixer represented by software instead of physical knobs & sliders.  I'm slowly but surely getting over it :)
 
Performance is as good as any interface I've used, and it's Rock Solid - not a single crash.
 

Thanks Bob. I am thinking, like you, that it is a lot of I/O for $300. I am curious though, if the line inputs go through the preamps or not, like the UH7000(which I read somewhere, so perhaps that's not true). 56 db of gain doesn't seem like enough, for my Beyer M160, nor the RE20, I'm planning to add, but I can use my pre's and go through the line in.
 
 Are you using the software screen to monitor levels(since there aren't "any" on the unit)? Or simply trusting that once you get your levels that you're OK?
 
Even if I look at higher quality I/O's, later on, this doesn't feel like a bad move for now.
Michael

For recording, I set levels according to the meters in Sonar.  For live play and direct monitoring, I use the Tascam app meters to make sure I'm not clipping, but the Samson sets the actual volume level.
 
INs 9 & 10 are switchable between line and instrument and have adjustable gain via front panel controls.  11 - 16 are fixed line inputs, although they can be set for -10 or +4 levels.  These are perfect for other devices that have their own level controls.
 
For me, this thing does it all great.  The only thing I can add is that B&H and GC/MF give you 30 days to kick the tires  :)
 
Before finding this, I was looking at 4x4 USB interfaces that were $200+, and I would still have the xtra mixer hardware inline.  I love being able to get something connected, tweaked and left alone.

There are separate line inputs on the UH-7000, but they go through the preamps.  Doesn't hurt the sound none.
 
Sounds like a best buy for the bucks w/ the 16X08

UPDATE:  After using the 16x08 quite a bit, I happened to notice a high percentage for System Interrupts in Task Manager.  In the 10+% range.  I could get this below 1% by simply powering off the 16x08.  Note that there were no real symptoms or problems to mention.  Just a bunch of CPU tied up.
 
Long story short, it came down to whether or not the USB port it is connected to supports mass storage; a new spec to me.
 

 
This got me digging into USB port specs for my machine.  The only ports in my system specs that mention mass storage are USB3.0.  I connected the 16x08 to one of these and everything still works great, but System Interrupts in my system are now mostly under 1%.
 
Apparently it takes special handling to move data for this many INs & OUTs.  :)
 
I'm still a happy camper that never realized there was something to consider, but now maybe I can add a few more Rap Pro instances to projects with the extra CPU cycles I now have available.  :)
 

BobF great info - I have made the purchase but have not - yet - taken my VS 700 I/O out of service...

I gave up on getting one, as my shop wouldn't have one till July at the soonest. I bought a Scarlett 18i20 demo for a good price and will sell my us1641 to recoup some of that.
I see the 18i20 as a good interim I/O, while I save up for a higher end one, like RME UFX or whatever else might show up "then".
Michael

Looks like the US20x20 is out ... with direct USB3.0 support.
 
I'm perfectly happy with the 16x08.  It's not I/O count that matters for me as much as variety of input types supported.
 
I've heard nothing but good reviews on the 18i20 ... 
 
 

Thanks for the heads up on the us 20X20. That is one of the first usb3 units I've heard about!
http://www.tascam.eu/en/us-20x20.html
Looks like an excellent model, with ADAT in/out and S/PDIF in/out. It does say it works usb3 or usb2, so I wonder what that actually means...    I don't see a price on that page. Perhaps their working that out.
Michael
I got my 18i20 last night and will be pulling out the us1641 after some errands. Looks nice! LOL