if your baby likes warm bottles, then we found that by putting warm/hot water in the bottle (but no formula) and then putting those bottles in an insulated bag (like a cool bag, cause they will also work to keep things warm), you can produce a bottle of warm water from your bag, add the formula, shake, and you have an instant bottle of warm milk.
Definitely only carry water in the bottle though, because a bottle of warm milk in an insulated bag will grow germs pretty quick.
But, it's much easier if you can convince baby that room temp milk is good
I have heard that about microwaves, SueM in MN, but figured if I heat the water in a microwave and then add the powder and shake, there shouldn't be any hot spots, do you think that is ok?
PLEASE, if you are going to use a cup of boiling water to heat a bottle at your restaurant table, be very very careful. I see this so often, and it always scares me. We saw a little baby knock over the cup last weekend at IKEA, and his mum had to rush off to the bathroom to stick his hands under the tap. I hope he was ok. Personally, I think it takes SO long to get the bottle warm enough this way, that it's just not worth the effort.
Bev