We have some LaCie's where I work and they are OK though we have issues with mounting and dismounting them from the Desktop sometimes when they are plugged in to 3rd part FW ports (ports that seem to work fine with everything else). Also the cases are not that sturdily built, even though they "look tough". After a few months of use sometimes it seems like the screws inside might be loose / make an annoying vibration noise.
Personally I have a G-Tech G-Drive Q which has FW400/800, USB2 and SATA on the back, and it has been a very good performer so far. Also it is more compact and more sturdily built than the LaCie drives, plus it has the nice "Cheese Grater Companion" look going on. Also quieter than the LaCie drives, which make a lot of noise when they spin up. The Q drives come in 160, 250 and 500GB models AFAIK. I would check it out before buying any of the large LaCie external drives. My next purchase for FCS scratch disks will definitely be Q drives. Plan to have a stack of 'em before the year's out.
http://www.g-technology.com/Products/G-DRIVEQ.cfm