Thumbs down to K2 Blackpoint
We have had a fairly tragic experience with K2 BlackPoint, and this is after trying to implement custom workflows in about 4 projects. There are some fundamental things you would expect the product to do OOB but it simply doesn't. Yes, there are some nice points. The real time view of the workflow is pretty slick. Integration with InfoPath is nice too, but seems every attempt to do something, you will have to jump over hoops to get there and consult numerous support articles. Support is average at best. You have to jump up and down to get heard. It's a complicated, buggy product that tries to do alot and ends up doing very little well.
- calling a custom web service or .net service is a pain to implement.
- Process Portal is very slow and lacks alot of features you would expect, like being about to delete more than one workflow instance at a time.
- we encountered numerous bugs with the product
- multiple K2 servers (load balanced) will cause you no end of pain unless you really know what you are doing
- they will charge you for UAT server lics
- Good luck if you use Kerberos.