I started with Permanents as a way to gain confidence for Brevets. You can cherry-pick the route (for example, a flat one if you don't like hills). You want to work on gaining confidence with hitting the controls within the time limits, and having your Brevet card signed and timed. They help you figure out what Food Mart foods work for you; how often to eat; how much to drink, etc. While yes, you have to commit ahead of time to the day you want to ride, you have control over the time you start - you can start an hour or two before sun rise to give you experience with lights and confidence with riding in the dark without really risking too much (if you get scared you can always kill some time in a Food Mart while you wait for it to get lighter).
They help you get used to working with cue sheets, and riding alone. You learn what you absolutely have to carry with you, and what you can leave at home. The risk of failure doesn't seem as big for a Permanent as it did for me for Brevet (which turned out to be all in my head).
When it's all said and done, the only difference between a Permanent and a Brevet is the group start. Go for it - what have you got to loose?