Yeah, a beta is always handy. I used to write in fandoms that didn't really have betas. I mean, even if you were friends with some authors, they could say they don't really do that sort of thing (beta, that is). I once wrote a story with another author and we had a good beta reader for it, but then she disappeared. We e-mailed her, but she just didn't seem to get on-line at all, we never saw her on AIM or anything.
Sadly, that's my only experience with a beta reader. But before she disappeared, she really helped.

But there's a freedom that comes with that
I know what you mean. When I first discovered slash, it was of my favourite band at the time and me&a fellow fan giggled over it. Then my friend came up with this odd pairing and I wrote a piece and it had ALL the bad slash mistakes. After that I've read that fic over & over, re-written it multiple times & it's kind of my darling.
(I'd give you a link, but my fanfiction site is offline, as the host is switching domains, plus you probably wouldn't know the band..)

When I was re-writing, I thought to myself "Well, I don't know them, so I can take what I do know about them and just take it from there". You can write your own interpretation of what you think&know they are like. I suppose that's what you meant with the freedom. :]