I was recently given an iPhone (was 3G, since upgraded to 3GS) to test out for a possible Blackberry switch. While the upsides are obvious (web, apps, fun!), I've found a few critical downsides...
<RANT>
1) Yahoo "push" mail doesn't push. Usually.
I've double-checked this with more than one iPhone and more than one account, but automatic delivery of email (push) from Yahoo simply doesn't auto-deliver. Usually. Occasionally yes, but usually no. So you have to remember to go into the app to fetch. Because of this, I've had some pretty important messages go unacknowledged for hours. Others have confirmed the same problem in other forums (incl Apple's), but for some reason it hasn't gotten any major net buzz. Unfortunately for me, I have two Yahoo accounts that I use regularly for personal and side business. My BB? It gets Yahoo pushes immediately and has for years.
2) Shortcuts? We don't need no stinkin' shortcuts.
Want to scroll to the top or bottom of a long page with a stroke or two? Use a BB. Similarly, cursor placement within a word just ain't gonna happen. Delete, retype. At least in 3.0 text manipulation is a little easier, but still way too convoluted next to the quick BB methods.
3) No visual message indicator.
For me, this is the real deal-breaker and why I'm still forced to carry around both the iPhone and the BB. Unlike every other cell phone and even wireless POTS phone out there, there is no way to tell by looking at the phone with the screen off that you've missed a call or have a waiting vm/email/sms. Why? Because Apple "Steved" the little blinky message indicator light. Doesn't sound like a big deal? Well imagine being the kind of guy who may receive critical and time-sensitive messages at any time, and imagine having to constantly pick up your phone, unlock it, go into email, and see if you have anything new. Imagine doing this every 5 minutes because you've now become paranoid that you've missed something important. Why? Because a couple of times you did miss something important. Now imagine being a guy who doesn't normally get time-sensitive messages, but whose wife got stranded somewhere and tried to call him when he was in the shower. Imagine his wife's fury when he doesn't get back to her any time soon, because he didn't realize he even had a message, having skipped his usual 5-minute checking interval.
</RANT>
There are always other complaints, of course -- there are with any device incl my BB -- but those are the three that really stand out and make my life much more complicated. And #3 is really the only one that keeps me up at night. Literally.