We've been supplied with five Dell laptops for use in the field. They are, I believe, M65 models. They've held up fairly well, so far, hardware wise, but their performance is spotty. To be fair, our issues seem to be more with how we're trying to feed pieces out of our trucks, both microwave and satellite. The weak link seems to be the Laird Inertia transcoders we're using for this purpose. Althought it's been 50-50 as to whether you'll succeed in getting your piece back to the station for air, reliability seems to have improved lately (moderate fall weather?).
Our IT guy says this particular model doesn't seem to work with most of the available transcoders he's aware of. Right now we have to use our cameras (Panasonic HVX 200's) as transcoders for recording pool feeds in court or NCAA basketball tournament sites.
I'd say laptops are fine if your company will a) listen to your suggestions as a result of your lively discussions, and b) research their capabilities and buy what you need in the way of accessory equipment to make them work. Having said all that, ours are still not as reliable as they should be, and I don't think having desktops instead would change that.