I think I may keep my HD7(and see what updates Microsoft has in store) I am really leaning towards the Arc as I keep seeing pictures....I'll see what Microsoft has in store and if I can't deal with Microsoft anymore(Which I currently love....the first time ever I've actually saw a phone and I am okay with being stuck with it for 2 years) and fall in love with the arc, I will get it....
I agree with Charlyee...I never really had many issues with mine...
My only issues/complaints were
2)Timescape had a few quirks(so does blur, sense, touchwiz,, etc)
3)Android 1.6(i blame at&t for this now)
Most of these problems could be overlooked and hopefully...HOPEFULLY, SE has learned the mistake with the Xperia X10 and will do better