Lets see... The iPad doesn't last a day, so even by your own standards it's not in the running?
But even with that there are several tablet PCs that can do what you're asking.
My Toshiba Point 510, running windows 98, with a solid-state drive in it (which is the only "hardware mod" I've done). It runs IE6 and Opera fine, plays MP3s, has no fans, runs 20 hours on its battery pack, and has a 7x9 display screen. It does weight a little more than the iPad (about twice as much) and is a little slower, but it's not bad for something made 10+ years ago.
There are plenty of other devices on the market, all of which have far better specs than the iPad. Does the iPad have a hot-swappable battery pack for continuous operation? No. Does the iPad have full Obex-style bluetooth functionality? No. Does the iPad have a shock-mount case? No. Does the iPad have a physical or virtual attachment system to allow it to dock and be used with a real keyboard/mouse and other hardware? No. Does it have USB or wireless USB/PNP support? No. Does it have speech recognition and transcription built in? No. All features of the tablets I've linked to here, all made in the past year.