I am a little late on this thread here but working with WWF long term may not be the best. It is a low level programming framework in which you can build code in visual format. It has no concept of human business workflow processing. You create loops, if then blocks, etc. You have to build everything from scratch.
I really see WWF being utilized but the ISV vendors like K2. K2 is building thier next generation product on WWF. WWF does not have the concept of a Destination User, Activity Slots, Escalations, Rules, nor does it have built in integration with ASP.net, InfoPath, BizTalk, SQL Server, CMS, etc.
Suggest you get it now if you want it because the cost will be going up. If you buy now, there are free upgrades, I can get you in contact with the right people.
Jason
http://www.k2distillery.com/