Well, you should use GSM (instead of 3G/Dual) while traveling to keep your battery alive, but you'll probably get a slow Internet experience. Still, its better than having a dead phone without a power outlet nearby, right? And if you need faster Internet speed, just switch to 3G and back when you don't need it anymore.

As for the wireless routers, I disagree - there are many situations outside your home where Wi-Fi can be useful. Where I live there are lot of free Wi-Fi hotspots one can use. Pass next to a school? Have a drink in a coffee-shop? Spend your time in the faculty campus? Even our Danube beach has good Wi-Fi coverage.

Your N900 can save these spots the first time you use them, so it can switch from 2G/3G to Wi-Fi automatically whenever you're within reach (with the default settings, Wi-Fi "wakes up" every 10 minutes - and you can change this interval - to check if there are any available connections - so spend some time at a location which has Wi-Fi and N900 will switch to it). So why use a slower 2G or battery-draining 3G (and even 3G is slower, depending on the net speed provided by the hotspot) when you can enjoy a good Wi-Fi without any big hassle of connecting to it?

Also, while we're on the whole Wi-Fi subject - I often use my N900 even while at home. You can't lie comfortably in your bed and read email with a desktop (or laptop/netbook for that matter) can you?

That doesn't mean 2G/3G isn't important, it is. And I wish 3G wouldn't drain the battery so much.