Multiplicity Pro is not part of ThinkDesk (you get the normal version Multiplicity which only let you control 2 computers and doesn't have cut and paste of files between computers, only a shared clipboard). The normal version is already quite useful, and you get a hefty discount for the Pro version if you own ThinkDesk.
KeepSafe is also part of ThinkDesk, and a lifesaver: https://www.stardock.com/products/keepsafe/
The two other programs are less useful IMO and there already are replacements in Vista (for ThinkSync at least). ThinkSync and SecureProcess are still in beta.
Please note that ThinkDesk in itself is still in beta and so you're betting on additional programs being added to it. If you only want Multiplicity and KeepSafe, it's going to cost you less to buy separately today. If you might be interested by future additions, then ThinkDesk is definitely the way to go (as you will get updates for "free" until it gets out of beta).
BTW, if someone from Stardock is reading this, you might want to change the wording on the KeepSafe Buy page:
ThinkDesk includes all of the following applications valued individually at over $100.00 for only $69.95:
-KeepSafe
-Multiplicity
Hum, not really a great deal if presented that way