Also on a mechanical keyboard you don't actually have to bottom out the keys like you do with a dome so they're a bit different that way.
On mine just a slight press will activate the keys, not even pushing it 1/3 of the way down, unlike domes where you actually have to make contact. This can help a lot with rapid key pressing and such.
Another thing is key rollover. On many dome keyboards you can only push like 3 keys at the most before it stops registering (possibly even making the computer beep at you) but with a lot of mechanical keyboards they can rollover more keys, so if playing a game and you accidentally hold too many keys it won't just refuse to work.