I love mine, but +1 on not using them in a tight group. You can have them on but don't ride in them unless you are pulling.

Weight etc: don't think that's an issue...
Syntace XXS is what I have - 330 grams and together with the risers to fit the oversize handlebar, they allow easy access to the top tube position.

They have given my speed in the flats such a boost. So yes, you shave off time. It's not just drag, it's being able to put your glutes into the game. and for a tiny incline, you stay down, pull on the bars and just hammer over it.

Yes, you have to have good balance and a beginning rider WITH aerobars is one squirrely thing to have in front of you. That's prolly why triathletes and drafting doesn't really mix....