PCs were curiosities until VisiCalc, WordStar, dBase, and even vi arrived. In the same way, PDAs were fun, but were initially just storage places for contacts and perhaps a few interesting apps. Cell phones were great because of their mobility -- a form factor. If you really want to make a tablet PC I'll buy, listen up:
1. The Media
The biggest problem with the future success of tablets is readily accessible media from as many publishers as possible. This means books, magazines, multimedia, and whatever we like. Nobody knows if we can go to a retailer, a captive Apple, Amazon, or whatever store to get our media. If it's just one vendor, then to hell with that. That vendor, by Murphy's Law, will instantly drop the content I'm looking for. Try it.
2. Video Playback
Hulu. Gotta watch it. Episodes of Mad Men. Gotta watch it. SomethingTube. Gotta watch it. Must watch it on this device with no latency and in at least 720p and in excellent audio modes. Which brings to mind: audio.
3. Excellent audio playback
This has to be accomplished either with great internal speakers (sorry about that, Mr. BatteryLifeEngineer) or fabulous earphones that you'd never leave behind on an airplane because they sucked so badly.
4. USED MEDIA
That's right. I don't care how it's serialized, and if we have to pay a micro-buck to some damn licensing company or not, but I want to buy used books, magazines, and even 'episodes'. Don't give me a bunch of crap about various theories regarding licensing and DRM. DO it. Or they'll get stolen anyway whether we like it or not. Mark these words and stop making your lawyers rich -- make yourselves rich instead. I'll buy that old Michael Crichton novel, but don't think of charging me full retail pop for it. Won't happen.
5. 3G/4G/WiFi For Free
I'm about to buy a bunch of freaking media from you. I want to download it, and I don't want it to take all day and all my battery charge to do it. Subsidize the account already, and I'll even watch ads in the corner of the screen while you download it to me. Got that, Macmillan?
6. SD or Similar Memory Slot
I have my own media. It's not your media. I want it to playback on this machine, whenever I want it to. Give me the slot. If you don't give me the slot and make me tether it to my notebook or phone, I'm going to hate you.
7. Auto-adjusting Display
Let me change it, or let me read it in full sunshine or in the dark of the subway tunnel. Period. Figure it out. Full resolution. Ten hours battery life. Wow me with 3D glasses.
8. Include the Keyboard
No, I'm not tapping on the screen. It smudges. Give me a lightweight ASCII keyboard with F-keys/etc so that if I want, i can use it as a netbook. No, it won't cannibalize your overpriced notebook sales. Maybe.
9. Apps. Real Apps.
Do not make me captive to your cloud-based apps. If I want to do docs or spreadsheets or whatever, let me do it. Let me use somebody's software other than your own to do this. DO NOT MAKE ME GO TO THE WEB TO DO DOCS. You are warned.
10. Make Me Return For Great Deals
Ok, I'll read that #44 best seller if you discount it. Or maybe watch that concert with nearly dead rock stars. But you have to give us deals. I'm not at the arena, and I'm not paying TicketMaster. I'm sitting watching a tape backup and might consider a nicely priced video of Sheryl Crow doing a concert. That's if I can pay for it easily and rent it for a few days, because you never know when you'll have time to read.