I'm all happy with my iPad, but when I talk to friends who are considering buying a tablet, all of them consider the Microsoft Office question because they work in Windows environment. So, that kind of compatibility will pull a few people, I think, as will a USB port.
I own a Transformer tablet and one of the things I want for it is a decent spreadsheet app. The one I tried sucked compared to Excel on my PC. Excel set a very high standard for me. After using it for 20 years, I have yet to see anything come close. I would love to have something that is at least workable on my tablet. The only ones I tried so far are Polaris Office and Google Docs. I haven't tried anything else as I don't use spreadsheets much as of late.
My vision of tablet computing is to have a single tablet that replaces your home computer. When your home, you drop it in a dock and it connects to your multiple monitors, printer, keyboard, mouse, etc. and you have a full on machine. When you leave your office, you pop it out of the dock and you have a nice touch interface with an iPad like experience but you still have access to all your desktop apps and data.
This is what I want as well. Right now, my Transformer with keyboard dock comes close, but I still need my PC for some things. My Transformer tablet can do probably about 75% of what I want to do on my PC and do many of those things a lot better or more conveniently. Right now I can do days at a time without touching my PC, but I do have to use it on occasion. A tablet-like PC replacement is something I would really like. I want to get rid of my PC completely. A phone plus a tablet is what I want to satify all of my mobile, communications and computing needs.