Vueling is fine, on a par with Easyjet (I personally wouldn't say vueling is better,eg the staff on Easyjet are always very friendly, with Vueling it is more hit-and-miss)
I've flown Vueling quite a few times, Easyjet well over a hundred ; that's to do with the routes I fly. On a trip to Milan I flew out Vueling and home Easyjet because of timings (and Vueling price was similar to Easyjet, which is not always true).
vueling had the advantage you could pre-pay a small sum to choose your seat (Easyjet is about to do the same so the only thing that was "better" to me about vueling over Easyjet has been smoothed out.) The disadvantage for me with Vueling re that Milan flight was that the size permitted for hand luggage is smaller than easyjet's and there is a 10kg limit (Easyjet allows 56cm height and no weight limit). So I had to take smaller of the two trolleys i use just in case vueling checked the size. however Vueling does allow a handbag/computer bag in addition and if you pay to check a suitcase the allowance is 23kg not 20kg.
edit. if you are flying a mix watch out on the hand luggage rules, the case dimensions aren't much smaller with vueling but it might matter
Edited: 6:32 am, October 29, 2012