Yumunum,
"-a file system"
I'm curious why you need a file system for? Saving files, Accessing files, sharing files?
iOS App suggestions: GoodReader, FileBrowser, etc all can save within the app (using on-board storage) with the WLAN radio or "Open-In" dialog box. WHen you begin to rely on a file sytem
"-you can search emails by body text. I can't even believe Apple doesn't have this in iOS"
This is supported in iOS ... you just need to use GMAIL as Exchange, not POP/IMAP:
server: m.google.com
domain: google
simplicity.
"-no physical buttons. Okay, this is more of a want than a need.

"
Well capacitive button for 'Home' I think is a logical evolution, but we're never getting away from Volume buttons or the sleep/wake/power button for a VERY long time; regardless of the platform.
Google Sync on mobile is still buggy on 2.3.4/5, what about backing up bookmarks and restoring?
Personally I still dislike having a GMAIL only account before I can begin using an Android device: Droid RAZR, and LG Nitro/Optimus LTE where the first two that allowed me to use the Android without using this first [SE Xperia Ard & SGS Captivate did not].
Still ... iPhone 4 & iPad 2 is a good pair - better if you don't own a laptop! You'll get more use out of the iPad that way.
It all depends on your use patterns, comfort, and real-world needs (not what you see others needs for those products). Personally I have an iPad2 testing from work over the past 4mths but I still cannot see/use it more than a weekend for a handful of apps.
I'm a smartphone guy and IP4 to IP4S was a good enough upgrade: superb camera optics (that alone was impressive), much faster HSPA+ data rates (real-world speeds in congested areas), less dropped calls, and for me about the same battery life (WLAN is almost ALWAYS on during the day and top-up charge overnight).