Personal Hotspot Solution
My previous device before iPhone 4 was the HTC Fuze. Best thing about that device was its endless hackability. I flashed so many custom ROMS onto that phone that I can't remember how many it was. Constant updating of the phone's capabilities and NO AT&T CRAPWARE.
But, because of the SIM/microSIM issue, I was wary about using my iPhone 4's SIM with an adapter in my old Fuze.
Finally, though, needed mobile hotspot and was unwilling to give up my grandfathered unlimited data plan. So I bought the best microSIM adapter I could find and slid my iPhone's SIM into the ol' Fuze with a newly-cooked ROM on it, activated its mobile hotspot, and voilá--instant unlimited-data hotspot. Thing sucks power like crazy, but if I keep it plugged in it's no biggie. Works like a charm and gives me full internet access in any hotel without buying their ridiculously priced wifi. Works in the car with the kid in the backseat playing on her iTouch. Now I can travel with my laptop again without sweating internet access.
I thought I'd given up that privilege by migrating to the iPhone. It's such a great gadget in so many ways that I didn't really miss the free wireless hotspot the old Windows Mobile device gave me--until I did.
You can pick up a Fuze or other similar 3g WinMo device on eBay for next to nothing. There might even be one out there I'm unaware of that uses microSIM natively so you don't even have to have an adapter. Then just go through the tutorials on flashing new ROMs on your cheap used phone, put one of the popular ones on there, and you'll have lifetime wireless 3g hotspot for the price of your cheap WinMo last-gen device. No recurring fees, ever. Sound good?