The real issue isn't whether you use gnomes in your campaign or not. Everyone's opinion and use cases are going to vary widely. The real issue is do you want someone else to make this decision for you or would you rather be making the decision of what races to include or exclude yourself? The same goes for classes or any other component of the game for that matter.
Also, the changes WoTC made to gnomes for 3E are horrible, though done in the art work mostly. That has been a huge contributing factor in the obsfucation of the gnomish identity. Just off the top of my head though:
1. D&D gnomes have large noses with an accompanying keen sense of smell (making them excellent alchemists - WoTC even retained this detail in the 3E rules, though the art doesn't reflect it).
2. They love gemstones for their intrinsic beauty rather than their monetary value.
3. They love pranks, jokes and general mischief (making them great, imaginative illusionists and tying them in with their faerie roots) and are far more jovial and companionable than dwarves.
4. They are defenders of forests and animals (faerie roots again) and in some worlds are inventors, tinkerers and builders. (Dragonlance did an excellent job with gnomes.)
5. They value family and clan and can be wickedly mean in defending both.
6. Evil gnomes are rare and particularly vicious.
Nothing the "designers" do will change the way I see gnomes nor would I cut them from a generic campaign. I have the benefit of having played in prior editions while newer players may not know gnomes this way because of the changes made to 3E.
Dragon Magazine once featured a series of point-of-view articles for each race. Most of these (not half-orc or half-elf) have been reprinted in Best of Dragon #3. They are highly recommend reading for understanding what makes each race really tick.