I'm glad I sold my iPad 1 a few days ago. Even though I have read some posts about improvments with iOS 5.1, I agree with bill_best and ballistic67 that each release just seems like a lottery and a crap shoot.
TBH performance has just gone steadily worse since iOS3, which was buttery smooth. One release of iOS4 had a wifi bug that wasn't addressed for many many months so I had to suffer slow wifi for ages,
I'd rather just have one stable app open at a time. Because Apple gimped on the memory for the iPad 1 that is all you can really expect from it.
I bought a cheap Nexus S at xmas and put ICS on it and I really find it much more responsive than the Ipad 1. I can do everything I need on the Nexus S, the only thing I miss is real estate. I also find ICS nicer than iOS.
Although Apple do make great looking hardware, I really think iOS needs an overhaul to keep up with Android.
So I'm either going to get the new Samsung tablet 11.6 that is soon to be announed or get a tab 10.1 for a bargain price and root it.
I wish everyone luck with iOS 5.1.