Thank you for the replies.

Juha, I was thinking of unlocking the phone and using local sim cards but regarding some of the issues that you raise: I figured since there is a way to mount it on the bike, that it would be at least water resistant and rugged enough but maybe not like their Edge line. I also do wonder about the crashes though. That's how I killed my last head light.

Dorkypants, I saw the article you mention. (RT @smartfone: INTERVIEW-Garmin mulls future of smartphone unit http://bit.ly/coFHoD). I guess, competing with Apple, etc is no easy task. Let's hope for better smartphones soon.

It seems to me from what you both say that my biggest concern should be the battery life. Thank you for bringing this to my attention as I hadn't considered that. There was one day when I'd arrived in a town as the sun was setting, having had a few problems along the way and if I hadn't had my phone to get directions to my final destination, in the dark too, I would not have been too pleased.

I guess I was hoping to get the confirmation I needed to justify the purchase. It just seemed so ideal to have both devices in one not just in terms of saving some cash but for the convenience of dealing with one device (weight, charging it, looking for it, etc.) Maybe just too good to be true. I might give it a try if I find it quite cheaply (EBay etc) at least until until something better comes up.

I'll keep you updated on my findings.