My girlfriend owns one of these scooters so I can give you firsthand experience having been driven it a few times.
1. It's made by Yamaha so you can google Yamaha Mio and should find plenty of info on it.
2. Shouldn't be a problem as far as repairs and spare part but I don't suggest taking long (2+ hr) road trip with it because it is a tiny little scooter with small wheels so unsafe on Hanoi's dangerous highway, especially when it rains.
3. The only probs she usually have with it have to do with the tires. This could be an isolated prob but in the past 3 months, i recall her having flats at least 4 times.
4. Again, it's a small scooter, targeted towards Vietnamese women (insert small size jokes here) so if you're a typical Westerner, you'd look and feel silly driving it. But then it's pretty light so parking, pushing up the curb is an easy task.

There you have it. G'luck.

Hey steph, I used to rent a mio in Saigon and it was great. It's a smallish auto, but still packs a bit of power. Me and my girlfriend even rode it to mui ne( 9HRS!!)
During the 6 months I rented it, I never had a problem. I am an average sized guy and i didn't feel to big for it. I say...go for it
Ps: thanks for your reply to an earlier post. I am settled in a nice place in town.
cheers, chris

I ended up going with a Wave, when in Rome and all that stuff. Was easier and cheaper to go this route. To be honest, I will be either back completely on a bicycle shortly or alternate between the motorbike and a bicycle. I have driven in many countries before (some in crowded Asian cities too)and its maddening and stressful to drive here so far. Bummer. We shall see, am giving it a month trial before handing in me keys. Thanks for all the info:)
Steph

Too late to respond to this, but the gear thing is the easiest part of riding a motorbike here. There's no clutch, you just kick the lever, and I've noticed a lot of people seem to just leave it in 3rd the entire time anyway. The hard part is having the ability to become a crazy, speeding, weaving, red light running, almost killing pedestrians, Vietnamese-style motorbike rider. I'm starting to think people either have that ability or they don't. I managed to pick it up right away, but I'm crazy so it works.