Not having flash on the iphone is inconvenient but in the end you deal with it because its primary function is as a phone. With the ipad, something that's supposed to be a media device, it kind of cripples some of the best of the best the web has to offer right now. I agree with thrik that there's more at play than it just being a resource/power hog (which I know about first hand because the shitty laptop I'm on right now shuts down from streaming anything flash for more than 5 minutes).
As lame as it is I'd rather have the modbook at this point. Only thing you really miss out on is multi-touch/3g/form factor. The mod book has a stylus and expensive wacom tablet in its favor.
http://www.axiotron.com/index.php?id=modbook ($1650, ouch)