I personally didn't feel like I wanted it, partly because the price, but also because IMHO, Psychiatry, while an extensive field is much less info than other fields such as Medicine. I felt that the problems you encounter in psychiatry 99% of the time are handled quite well in Kaplan & Sadock and a good attending to answer your question.
Medicine on the other hand--well Up To Date was needed. There's too much info and too much progress going on. Harrison's, the equivalent of Kaplan & Sadock for medicine is too much to read. UTD often had better info than the attending.
I haven't tried psychiatry online though so this could be a case where had I actually tried it, I might've liked it. It'd be nice if someone here who used it could give is their experience with it.
I've used it. It's not really analogous to uptodate at all. Uptodate writes its own referenced--yet opnionated--synopses of recent research on a particular clinical topic. Psych online is just a portal that lets you access different resources: journals, textbooks, guideline, etc. It doesn't really have anything that a good university hospital wouldn't already have via remote access-- it just puts these resources in one place for easy access and provides its own search functionality.