I got in on an IK group buy that added VIs as it went til it was TW2 two years ago, and the price hasn't moved any since, so don't miss out!
I know the stuff isn't 64 bit at the moment, but as Squids has mentioned, everything is backward compatible with and will sound even better
in ST3 which surely will be. Surely.
There's a staggering amount of material in TW2, and just in Sonik Synth or SampleMoog alone. There are dozens of raw waveforms from legendary synths too (moog, oberheim, sequential, arp, emi) and a great set of quick to use parameters and effects for making your own patches. And when you add in ST XL and Miroslav you have all the basics for making music in nearly any western style.
But if you like a little more sonic spice, the World Instruments and World Grooves are excellent choices for your free libs. WI features stringed, blown and struck instruments from Kentucky to Kilmanjaro, many with velocity layers, rolls, ruffs and special noise techniques exclusive to each one. And the Grooves are well produced loops that feature some really talented percussionists in a variety of world styles and tempos. They make a great pair together.
If you need some great pop sets, try Hip Hop Instruments and Electronic Drums. Both have a lot more than their titles imply, with great strings, guitars, synths and basses in the former, and BIG movie toms, fully produced electro and acoustic kits and menu maps of MANY famous (and infamous) drum machines of the 80's and 90's.
BIG NOTE, if you buy one of the $10 Xpansion Tanks at eSoundz, it gets you the crossgrade price for TW2! Just don't choose Acoustic Piano 2 though, it's 99% identical the pianos in Sonik Synth 2. So don't waste a choice!