I'm not sure what the crewsaver jacket is. I use one of these (also available from other shops!):
England Survivor Life Jacket - Sportfish It's very comfortable to wear - I barely notice it's there. Only drawback is that it must be worn outside all other clothes so it can inflate freely when needed, so it can get in the way of your pockets/waistcoat. Course, if you're in a boat, you can have a big bag with you and not need your pockets. You can get combined waistcoats/life jackets but I seem to recall that they don't have quite as much buoyancy.
Some folk prefer manual operation as opposed to automatic. Me, I went for automatic.