It's a matter of what you'll use it for and whether or not you actually will use it. I would think that a 3G Kindle would be a good alternative if it's mostly for ebooks. The 3G subscription is free for life with the Kindle (that in itself will quickly pay for it) and although the e-ink display is too slow for animated web pages, it means that the battery life is about three weeks between recharging. The iPad's battery life is measured in hours and minutes. There are other tablets like the Cruz and RIMM's tablet that will do everything that the iPad does plus Flash and they have SD slots so you can add GB's to them. From a functional viewpoint, there's better alternatives then the iPad but the iPad is cool.
Not even close to worth it.
Three or four years ago, there were tablet computers made that sold for cheaper and far surpass everything the ipad can do.