Small and compact but with more options to upgrade than a lap top, the Shuttle, for the money, it is pretty good and it is a nice small machine that can pack a lot of punch.
Quad cores were played around with, but got way to hot, duel cores were the way to go, but graphics cards were an issue, can be quite tricky getting a good one that'll fit.
Also sticking parts inside can be tricky as there isn't much room. There is plenty of usb sockets which is handy.
Placement of the thing is important, because it gets hot, really hot, well to be more precise, the air it kicks out. If you keep it by a desk and keep sweets in the draws, they could well melt.
Using the machine as something to take home if you have the option of working from home with work hardware works quite well, but it's a lot more hassle than originally expected, mostly because there isn't much room to plug and unplug the stuff out back, perhaps if there was a quick interface thing along the KVN line that would be great.
As it is, I'd prefer a dedicated work and home rig, but I wouldn't want to use my home rig for work purposes, software licenses being one of the problems, that and it is just easier having a rig all set up to work with source control that IT can figure out etc without being your responsibility.
Working from home is great option, especially for people with families or those who have a long commute, but just allowing it isn't enough without offering to really support it.