I'm thinking of making the plunge, $400 is a lot for me but with 36 months interest free at Sweetwater it's almost too hard to pass it up.

If you've got it what's your thoughts? Does it live up to the hype? How does it sound? Does it play well with Sonar? Is it worth the price in general? Another question is, how does the core library sound? I'd like to only put as much in my hard drive as I have to for now until my next upgrade.

Addictive Drums and even SSD just don't do it for me any more (AD2 never really did). I'm thinking about doing some side work for local musicians who record at home but want better drum sounds or ever program drums for them, so SD3 would be ideal I think for that. Also thinking about offering re-amping through my Axe FX 2, but that's off topic.

It's a game changer IMO...

It's perfectly fine either stand alone or in Sonar.

I've been using it since Sunday and it is heads above any other drum software to me. The sounds are really good and very tweakable. It's better with E-drums than before. I'm still learning it, but so far a very happy customer.

Just the new  kits would have been like buying 2 full SDX. And you have mallets, rods and brushes on so many I have taken the Roots Mallets off my list. They sound great and I haven't even downloaded the Surround parts. There is so much that is wonderful I thought I would mention the 6 really good kits. Did Toontrack have a Yamy kit before? I don't remember one. Groove3 has a 4 hour(I believe) tutorial on it and I've been working my way through it. I think I paid $147 for it and it has a ridiculous amount of value for that. It was a long wait but now that it's here, I sure can't say I'm disappointed.

I played with it all weekend. SD3 is amazing. 
The sounds are killer. The ambient mic recording is perfect. You can dial in whatever you like. 
The system resource use is minimal for what you get!
Drum pattern editor is great. 
My old Roland TD6 plays great with it. I wish I had a better controller but it didn't stop me from jamming and having a great time. Love this thing!

I've got an old Alesis USB drumkit and this is the best I've ever got it to play/sound with SD3. Still not great, but better.

BassDaddy
Just the new  kits would have been like buying 2 full SDX. And you have mallets, rods and brushes on so many I have taken the Roots Mallets off my list. 

My thoughts exactly. I've been putting off getting the brushes and mallets for years. The infrequent sales and my wallet were never quite in sync. Now I'll get those plus a bunch more kits - and a tambourine(!) - for 200 bucks.
 
I haven't bought it yet, as money's tight ATM, but my birthday is approaching and my socks and shirts from last year are still serviceable.

I haven't jumped on this yet because although it will be nice to have all the bells and whistles in one interface I can do everything I need with what I currently have (Ezdrummer 2, SD2, AD2).  New kits are always nice to have but if I can't make a good song with the 15 or so I already have then it is not my drums that have the problem.
 
I will most likely will get it later when/if it goes on sale.

"...if I can't make a good song with the 15 or so I already have then it is not my drums that have the problem"
 
Well said. Same principle applies to sample libraries, compressors, equalizers and reverbs. And yet, a new analog tape emulator gets introduced almost every week, go figure.

bitflipper
"...if I can't make a good song with the 15 or so I already have then it is not my drums that have the problem"
 
Well said. Same principle applies to sample libraries, compressors, equalizers and reverbs. And yet, a new analog tape emulator gets introduced almost every week, go figure.

The have (at least) me sussed?