I own the le Avengers and have played quite a few games on it. I have to say of all the NIB Sterns I've purchased I got bored with Avengers the quickest.
I find myself in the same predicament nearly every game. I have IM and Black Widow left to collect. And seldom do I collect them all. So at that point I'm always having to manuever the ball and shots so I get left flipper shots to take on these two, sometimes I can hit IM with a backflip with the right flipper, but not often. It gets more discouraging that I nail the BW ramp and it doesn't clear, and I did the adjustments on it that I read here, except I haven't done the plastic adjustment yet. Sometimes I can do a threesome shot on IM and that is very satisfying, but in the end I just am getting bored with it and like some others, going back to Xmen and even Transformers. Tron never lost the appeal either.