One of the better (and fewer) FREE forms of entertainment on the Vegas strip- also a tad more kid-friendly, for those of you who actually think that kids somehow belong in Vegas. Not exactly sure how that works, but sure. Kids like water. And flashy things. And things that move. Skip the burlesque show and bring 'em here.
Only saw a few fountain shows while in Vegas- of those, mostly country-ish and traditional songs were observed. They could probably make it more interesting if they were to choreograph the fountains and lights to something more modern, maybe 50 Cent's "In Da Club"? I suppose it would lose it's kid-friendly appeal after that, though. :D
Definitely watch at night. The addition of the lights alone make it worth it's weight in gold. It's also a sight to see from the top of the Eiffel Tower at Paris- a different perspective entirely, although you'll miss out on the misting of water from the splashing of the fountains if you were to opt for the view from the ground floor. Word to the very wise- bring a jacket if you decide on the view from the Eiffel Tower at night. It gets chilly (and windy) up there. But totally worth it.
I always hear that Vegas is one of the most romantic hot spots ever. I don't really get that, but those who think so must've been factoring in the Bellagio fountains. Definitely come here if you're into mush.