I only just bought the game and am in the very early stages of playing with it. So take what I say with a grain of salt. But I have found a few mods that I think are worth looking at.
1) I use the 1.6 version of this damage mod and it's good because if you get too close to another car, you will do damage to your front wing (unlike the fake damage to the wings in F1 2010) and also if you hit a wall (I also assume another car) too hard you will destroy your suspension taking yourself out of the race.
http://www.racedepartment.com/f1-2011-mods/66402-download-realistic-damage-i-human-updated.html
2) I drive using the cockpit view and the default cockpit view does not appear to tell you how much KERS you have left in a lap. So I find this cockpit HUD to be very useful.
http://www.racedepartment.com/downl.../cockpit-view-hud-extra-view-choice-fov-5706/
3) I believe this tire mod might be worth looking at. I have not driven with the tires long enough in a session to see their wear, but a trip through the gravel does show up with this mod fairly well.
http://www.racedepartment.com/f1-2011-mods/66315-download-rddev-inproved-tires-2011-a.html
Finally I have downloaded an all important AI mod, but I have yet to install it and to tell you the truth I am not even remotely qualified to tell you what AI mods are good in F1 2011. So I will defer that answer to someone else.