Thunderbolt Initial Setup / VZW What to avoid

yes, you can enable the backup assistant later. you'll simply go into settings than "accounts and sync" where you'll be able to set it up.
i think it's debatable whether backup assistant really drains your battery, but there is no point in having it when your data is being stored/backed-up into google's wonderful cloud.
 
I've had problems with the cloud contacts saving when I had the blackberry. I would have duplicated contacts and also notice that Google contact list wouldn't be as up to data as backup assistant was.