We use SafeGuard which is now a Sophos product (was Utimaco), centrally managed etc.
I've used Utimaco products for yonks in various guises on PDAs and laptops, and whilst I wasn't involved in choosing the product at my current place of work they decided to go with SafeGuard.
It's not bad, the downsides with it are the same as with all enterpise type products it seems, the good old challange response and pre boot authentication causes issues with some idiots, sorry I mean people
Where my other half works they use safeboot, she hates it. We had a new starter the other week who said they used safeboot in their old job and what were we using, he said he was glad it wasn't safeboot
Performance has been fine, there's no real difference once the initial full encryption process has completed, which takes around 3 or 4 houts for an 80 gig disk, scale up accordingly. However all these laptops are only a few years old, they are either Lenovo T60, X60 or X61 units.
I've also been asked to look at some 'stonewood flagstone' hardware encrypted discs, we need some new laptops and Lenovo are apparently offering these as an option. Got a chap coming down to give us some roadmap meeting next month so will see what they can do.
Hardware encrypted units potentially seem so much less hassle so I'm hoping they are actually decent!