I used my Avent bottle warmer religiously when at home, and would bathe bottles in a jug of hot water when at other people's houses - microwaves were my absolute last resort with DD1. Everyone else I knew just used microwaves lol, by the time DD2 weaned herself and started on formula I just cbs buying another one and would instead prepare bottles by heating bottles of cooled boiled water in the microwave, then adding formula after warming so as not to stuff with the nutrients, itms?
I personally found the bottle warmer to be one of the best gifts I was given (mum scored it for me from a friend of hers so it was second-hand), but by the same token it was just as easy to use the microwave and water method that I used with DD2, so it's up to you