I dont play games, so none on any of my iPads either.
I read lots of news and tech blogs on Safari, and I open multiple tabs while I do that. That's when Safari would crash on me with regularity on iPad 1, which I bought on debut day of the 3G model. I've continued the same reading practices on iPad for going on three years now, and I noticed crashes (as documented on my diagnostics logs on iPad 1) starting with iOS 5. That was noticeable across the years I've been on iPad, and I had comparison against iPad 2 and 4, which I still own.
iPad 2 has double the RAM of iPad 1, and iPad 4 has four times the RAM of iPad 1, which is the problem that I've observed with older models.
Between my husband and me, we owned three iPad 1s, which we've given away. I see more crashes on iPad 2 as well, though not as many as on iPad 1, and later versions of iOS 5 eased the frequency of crashes, but not to the level of restoring original performance. Apple issued updated versions of iOS 5 quickly, probably because of many complaints. I suspect that even with the upgrades, iOS 5 is pushing the limits of iPad 1's hardware, which is why Apple has stopped updating firmware on iPad 1 altogether.
I liked my iPad 1s fine for a long time, but performance declined, and I wouldn't buy one now. If budget doesn't allow the latest models, the lowest I'd go is iPad 2, which at least Apple is still selling, and which shares some older parts with mini iPad, which is a relatively new product.