If you travel out of the country a lot like I do, you need a Blackberry. Here's why.
I was in Taiwan and Japan in December / January and used email, web and apps (Twitter, Facebook and others) pretty much constantly on my Verizon Blackberry Bold 9650. The total data usage was 40MB in Taiwan and 20MB in Japan -- not too bad, because Blackberry web and email are so efficient in data transfer (read: intelligently compressed at proxy). My total roaming charge for data? $0.
I'm on the $64.99/mo. unlimited international email, web and app data plan, which some people consider to be expensive. But consider what would have happened on an iPhone. AT&T's "affordable" [international data packages](http://www.wireless.att.com/learn/international/roaming/affordable-world-packages.jsp) are as follows:
Using 60MB of data would have cost an additional $119.99 (per month) over a domestic data plan if you had the foresight to sign up for the 100MB plan. If you didn't and say, signed up for the $59.99, 50MB/month plan, you would have ended up paying $59.99 plus (10 * $20/extra MB) = $259.99. If you hadn't signed up for any international data plan, 60MB would have cost an obscene $1,200 (60MB * $20).
This isn't all. The iPhone is like a real computer, which means that it connects directly to all of the data services you use. If someone embeds a 500KB image in your email, it downloads the entire image, and you get charged $10 for the 0.5MB transfer.
In countries with low data quality of service, it is likely that an iPhone trying to connect to your email server via POP or iMAP may never even finish negotiating the handshake required to start receiving or sending data. I was in India with an iPhone, and a Blackberry downloaded 100 emails before the iPhone started downloading its first email. Even though I used the iPhone lightly, I blew through 20MB in 3 days, leaving me in a bad situation for the rest of the 3.5 week trip because I had signed up for the 20MB monthly international data plan.
If you live in the states and travel internationally, spare yourself the burden of trying to use an iPhone or Android device overseas. Get a Blackberry.[^1]
[^1]: If you're on Verizon or Sprint, make sure you get a Blackberry with both CDMA and GSM so it roams properly overseas.