The studio has the Dolby Surround Tools software running on a few of our systems, but I've only used it in one of the rooms. Not all of the rooms are set up for surround sound mixing, as only two of them have the capability to be turned into a room with this ability. The computer we're running it on is an Apple PowerPC G5 that has 8.5 GB of RAM and dual 2.3 Ghz processors. It's a Pro Tools HD system, so I can't say I've ever had a problem running it, although I've only used it on a handful of occasions.
Dolby Surround Tools is really a must have for anyone who wants to mix for post production. It's great that Dolby has made a tool like this for those out there using Pro Tools, as I don't believe it would be possible without this. It's not too expensive when you consider what you're getting and what you couldn't do without it. This is definitely more of a necessity thing more than anything else, but if you do need it it's nice to have a great option like Surround Tools has to offer.