I downloaded it on my ipad 1 last night and lost my jailbreak but I really wanted it. It runs fine I would say a little faster. I love the all the new features. safari doesn't reload every tab now like before. Everything just works with great new features.
Great news! I assumed it would run well on the iPad 1, but hearing that the new features make it a better experience is great to hear. The part about the tabs no longer re-loading every time is the best. It is the thing I like the least about my iPad.