We've been using AccuRev for a few years now. It's a serious improvement over our last tool (Razor) and while I'd recommend it for others- it does have a few drawbacks.
Benefits:
- The stream based interface is quite intuitive. I make snapshots every second week and have a number of ongoing development streams branching off the snapshot.
- Moving changes between stream is really easy, just select the change, send it to the "change palette" and select the destination stream. It guides you through all the files that need to be merged.
- The command-line utilities are great. We've managed to script most of our release generation around it.
- Integrations for Visual Studio, Bugzilla, etc...
Drawbacks:
- As monjardin pointed out, the client GUI can be slow. I use the windows version for all my history/stream searching since it's much faster than the X11 one. Of course, the GUI's written in Java so performance obviously wasn't their first concern.
- It's starting to get slow for really large databases (I'm talking over 300,000 LOC), although they've apparently addressed it in today's release of 4.7.
We opted to go with the cheaper license and not get the change packages feature (I can't see them working that well anyways, as the entire idea of promoting individual changes flies in the face of continuous integration). So far it hasn't hurt us.
Overall, for the price you pay it's a nice tool. We evaluated ClearCase, MKS, Spectrum and Subversion during our trial period. Subversion may have been a good choice, but it was still pretty green when we were evaluating. I've never heard of Plastic before, but I regret not evaluating Perforce.
Also, I understand that the engineers over at Trolltech (makers of Qt) have recently switched to git. I'd be interested in checking that out as well.
