Werk recently bought a handful of HP DL380 servers. They're really good.
HP/Compaq have really thought about this machine. Everything about it is really well designed.
First of all, the physical aspects of this machine are great. It's a 2U rack mount, with absolutely the best rack mount kit I've ever seen (on anything that's been near a rack). The rack rails clip into place - you don't even need a screwdriver. Then, just slide the machine into the rails. The clips that hold the machine out are a bit fiddly when you want to push the machine into the rack, but they're not the worst I've ever seen. The machine has two big thumb screws on the front which screw in perfectly to the rail front - none of this fiddling about trying to align the screw with the hole.
In the rack and in use, the machine is really good too. The built in raid controller is really nifty (our machines all have 2x36GB (mirrored) disks in them). Like all such controllers, it's a bit slow to initialise at power on, but seems to work beautifully once it's got past that. It's all hot swappable, as you'd expect. I haven't had to replace a disk yet, but I'm sure it'll be easy enough to get the new drive in and working.
HP have built in some kind of support for different OSes. The SmartStart thing does what ever it does with Windows, or can be switched into Linux mode, where not much happens at all (because it doesn't need to! ;-).
Running, the machine flies. I know it's all new and modern, but it's designed to be good - fast CPUs, fast buses, fast memory etc. You can stick in a second CPU if you want as well - that would make a seriously kick-arse system. You can also put in up to six disks, two power supplies, three PCI cards and oodles of memory. It's a machine to build something big with. This level of expandability means it'll be useful for three years or more - good news for obtaining budgets. There are three year support options too, so clearly it's all arranged with the bean counters in mind.
Servicing the machine is really nifty too. All the failure-prone components have status lights - inside, the fans have good/bad lights, so does the power supply and the disks (there's no stupid interlock stopping you running the machine with the (single clip, no screws) lid off either). The machine also does a lot of self-checking. I mistakenly didn't seat the PCI riser properly- a little red light comes on at the front of the machine and it refuses to power up. Even the PCI riser is quality. It's got two swappable slots, and one normal slot. Again, you stick the card in, and it fits perfectly - not like cheaper kit where the L shaped metal thing doesn't quite fit and you end up holding it under tension while you screw it down. Once you're all happy, just slot the PCI riser back into it's rails and do up the two thumb screws. It's really good.
All in all, the HP DL380 is all designed for maximum uptime. Everything about it is good quality and well designed. All this, and it's not stupidly expensive either - easily worth it. Now, if only we didn't have to run Windows and Exchange et al. then we could have uptime to die for!