Here is my two cents worth.

I just put aero bars on my new bike. My main reason was to do better in
Tris but because of life haven't been able to do any this season. I left the aeros on anyway mainly to get used to them - they do take practice and time to build up confidence.

A month ago I did a 3 day 165 mile tour and found I LOVED the aero bars. Having the optional positioning was a blessing. But as RoadRaven said they are NOT for group riding. Any time I used them I was by myself on the road and we were not pacelining.

FYI - just for fun. Last Wed night we were on a 30 mile ride and for the last 8 miles I went down into aero and picked up 1.5 mph so we were averaging about 19 mph - a friend (who always drops me ) was riding behind me and kept hollering out - "slow down! you are an animal - you are killing me" Where is the evil smiley when I need it?