I use Rolad V-Drums at my "project studio" - since I do not have a good sounding drum room. In addition to the Roland sounds (most of which I have "tweaked") I also trigger Alesis sounds and to a less degree, some samples.
In other studios I may bring my V-Drums or I may bring one of 3 accoustic kits (Maple, Birch, Mahogany) - or a combination. It depends on the project, the room, the mic's available, etc.
In most cases, the electronic sounds are good enough for demo's, jingles and even independant CD projects destined for mastering. In particular, the snare sounds and kick sounds can be tweaked to sound very real. Toms are more difficult and electronic cymbals pretty much suck, no matter what you do.
It's a trade off (like most things in music and in life). Do electronics sound as good as a great kit, properly tuned, in a great sounding room runing through great mics and great pres? Probably not. Do they sound good enough for the majority of projects done in home studios - I think so.
It all depends on what you are looking to achieve. However, I have noticed (and have heard this from others - including our own Blue Bear) sometimes the electronic drums don't sit in a mix as well as real drums. For lack of a better word, the e-drums don't have the same "presence" as real drums - (in particular with tom sounds.