[Zak]

There is no reason that iPad software won't be as sophisticated as current desktop applications like Excel.

Yes there is. Apple seems pretty intent on keeping their policy of forbidding interpreters, plug-ins, virtual machines and the like. To really be as sophisticated as Excel, a program must include a scripting language and extension mechanism. That's not to say that a spreadsheet without those features isn't just as useful to most users, but it certainly isn't as sophisticated.

Apple may, of course ignore the rules it requires third-party developers to live under when building its own software.