The most detail is here
http://www.ikmultimedia.com/products/sampletank3/index.php?pp=sampletank-3-info I would like the improved Miroslav and a better, 64 bit engine to use some of my existing content, but at the upgrade price of $99 the jury is still out. It looks like a good application for the first time user, but I am not sure its aimed at me.
If I was using ST3 I would probably bypass the inbuilt T-Racks / Amplitube based effects and use effects in Sonar's FX bin or FX chains, which may or may not include T-Racks and Amplitube, so that part of the package does not sell it to me. Like instruments that use built in effects in Kontakt inbuilt effects can actually slow down the work flow when you have to go in an bypass them.
I am not sure about the MIDI engine or indeed the concept of running MIDI patterns within ST3. In my drum samplers I only use the built in MIDI player for auditioning even when there is a facility to chain patterns into songs or song sections. It does not seem like a convienent workflow from my perspective when the DAWs track view and MIDI editing is so powerful.
I am not in the market for new "bread and butter" content but I don't think the question was ever answered about how much of the 33GB is actually new, if you read carefully IK do not imply that it is 33GB of new content, but some people have read it that way. We know that a lot of the orchestral instruments are re-packaged and re-scripted Miroslav samples.
I wonder how much ST2.5 stuff is also repackage.
For your convenience — and to avoid the hassle of converting your previous SampleTank 2 XL sounds — all of those prior sound libraries are included in SampleTank 3. Already imported, properly categorized and easy to access, previous users will immediately find sounds they are familiar with. And new users will have an additional arsenal of bread-and-butter sounds that have made history.
Then there are a lot of loops, that must take up quite a few GB. I would not use them, will the installing them be optional.
To me it seems closer to Dimension Pro than Kontakt.