Most of that do any time of training or consulting typically use laptops, and they are even reasonably common in the corporate world - even for those that have 'desk' jobs. I have a couple desktops at home, but I've used a laptop for work for close to 9 years now. No complaints, let's me do most of what I need to do.
But my laptop is pretty junked up now, you know how it is. You install what you need, try the odd piece of software, next thing you know it takes 5 minutes to boot. For a while everytime I closed Explorer I got an error message, finally an update fixed that! So it's time for the old format/reinstall and/or buy a new one.
We bought a desktop for the office for dev work, just a vanilla Dell Vostro with 4g RAM and dual video cards, dev work on that machine is definitely nice! Ran about $1000. Chris - our developer - very happy with it plus dual 22" wide screen monitors. So, thinking that if I bought another desktop and configured it just for dev work (I do some here and there), that would ease some of the pain of cleaning up the laptop. So, buy another Dell, or ?
Decided to get off the corporate path, bought a machine from cyberpowerpc.com. Quad processor (yeah, a real four way, no tricks), 2G of memory, dual 512m video cards, no OS - out the door for about $850. That's a lot of machine! Paid $10 extra to get the clear panel and internal blue lighting, but other than its just nice. Plenty of ports, drive bays, even has ports on top of the machine - handy because it sits under the desk. I've just loaded XP SP2 (sorry MS, no time for Vista) plus VS 2008 plus SQL 2005 and patched it all, should be interesting to see if the software can make sure of the hardware. I know 2G not a lot of memory, but easy enough to add 2 more if needed.