I play an Aasimar (ECL +2) and have got him to level 8. I would agree that playing ECL characters is tough because you have to take on a server that is already renowned for its difficulty, and multiply that difficulty by having to do content under levelled. In my opinion this is the root cause of player's frustrations, and not the extra xp required to get new levels.
Now in general ECL classes are tough. However I wouldnt change ECL too much, except for perhaps making characters not count as +x levels higher for the purpose of getting xp from enemies. Taking longer to get levels doesnt seem bad at all, if you are doing it versus at level content. However having to fight things +x levels higher than you to get xp certainly makes everything much more painful, and is in my opinion the root cause of player's frustrations.
Now in the case of Aasimar in particular, I would REALLY like to see them brought down to ECL +1 like in the literature. After playing this far, I have a little rant. The extra feat and skillpoints they get doesn't feel like it justifies the ECL +1, and I personally would opt out of it for ECL -1 if I could. The second ECL feels like overkill.