Well for one you don't want to be doing certain things on public WiFi hotspots (banking and anything you want to keep secure).

Secondly, some people still have Cable and DSL internet connections that are much slower than their phone's LTE connection in their markets, ESPECIALLY for upload speed.

In the case of DSL, if you're instant-uploading all your pictures when your phone is on WiFi/Charging it can cripple the download speeds for everyone else on yoru network (i.e. have fun trying to stream a 720/1080p video on YouTube, and that movie you were just streaming through your Netflix XB360 app, it will buffer perpetually now gratz!).

Unless you use a metric ton of data streaming stuff from Google Play (in which case you're better off just getting a cheap 16GB SD Card or just buying a bigger storage SKU iPhone), 3GB isn't bad and should handle pretty much everything you need to do, with few exceptions.

Another huge issue with Android devices is Google Talk Voice and Video chat being blocked on AT&T's mobile network.  They've never allowed this to go through without hacking your phone, but iPhones are now blessed with the ability to do this over HSPA/LTE now...  Hilarious...

With the way AT&T cripples their phones, I'm starting to wonder why it's even worth it to have a smartphone, instead of a cheap feature phone on some cheap network like Boost or Sprint for 1/3rd the price and just getting text notifications for everything...  I think I'll be going to verizon in a month or so to get a device that is less crippled though.  The bloatware isn't even a big issue since the only thing I can't disabled or Uninstall on my Phone is AT&T Ready to Go and that's fine.

It's the way they block and lock down features that is a huge issue, and the only workaround is to run more apps/services on your device which impacts it in other ways that aren't good (i.e. eating at your battery).