Generally I've found that if you go for something built from MDF they hold up fine structurally, but over extended time you can cause wear to the "effect" that is stuck on the top of it.
This kind of wear could create quite a nice effect on a solid panel desk, or alternatively can be sanded/varnished again to remove anything you don't like the look of.
Also, as/when you want to move the desk, something with a veneer on it will almost certainly scratch or peel in one place or another unless you are really careful, so that's something else to consider depending on how long you want it to last.
Ikea do some decent solid wood tabletops that you can then attach legs to, it might be worth looking at going for something like that instead.
Always good inspiration for what you can build found here too:
http://www.ikeahackers.net/