No AppleTV serves a pretty different purpose. And even if an iPad could do what AppleTV can, you'd have pretty much no way to connect it to a TV. (That HDMI connector sucks big ass)
AppleTV opens it's wings when you own some more Apple products, and when you live in America. So much features are blocked, here, in Poland, and American prices are so much better. Even with those cons, I'm really glad I bought an Apple TV 3.
And remember that ATV2 can't display 1080p content (720p is the cap here), but on the other hand, ATV3 can't be jailbroken (yet, but I've heard that pod2g has an entry point). Can't have everything ^^