To the OP - I also have the PCM-M10, recently acquired. In testing it out, I've used the internal mics as well as a CChurch 9100 preamp and both the CA14's and CA omnis. My comments on both:
The Sony internals are surprisingly good. I'd guess they beat out most of the internal mics out there. In situations where I'm grabbing and going and don't want additional gear or have no ability to use a stand or clamp, it's pretty good on it's own. I'd say similar to my MicroTrak, battery box, and Sound Devices omnis. Maybe a little less crisp on the high end. The big drawbacks are the omnis at shirt pocket level pick up any surrounding chatter. I don't know about you, but at festivals and concerts there seem to frequently be those folks who decide now's the time to regurgitate every stray thought and experience with their friends, in complete disregard of everyone around them. With the omnis at body height, you're probably going to get more of that than you like. Just the ability to put a pair of omnis at any distance above that chatter will add significantly to your ultimate result. Or getting the M10 above the fray.
I can hear a significant difference, however, when using the outboard preamp, both with the omnis and cards. SPL and overload could be a problem in some venues, but probably not in the one you mention. I did hear much clearer sound with the preamp and outboard mics (bass that was "punchier", highs that were "crisper"), so I think you'd be pleased with those as an option. I like my Church-Audio gear and think it's off the charts in terms of "bang for buck". If you've got $200 or $250 to spend, that's the best place to spend it, in my opinion. Get an inexpensive stand, some wire spreaders, and drape split Church Audio omnis at 10' or more above the crowd and you'll probably get a recording you look back on year after year and enjoy. Just don't set up anywhere near the beer tent <grin>.
To Eliezer - It may not have been your intent, but the language you chose in your posts (referring to others as behaving like children, denigrating their decisions, demanding specific responses, suggesting that tapers are just looking to screw over artists and not buy CDs) is pretty offensive to the community who posts here. You are entitled to say what you like, but if you offend your audience, you shouldn't be surprised if they return the favor.
As to a convincing reason why we tape or what we do with our tapes, I can't speak for everyone but I can speak for myself. Part of it is the creative process of trying to achieve the highest quality and best sound I can - hearing a good pull just once gives me a feeling of accomplishment, because it's not easy. I think I would enjoy being an audio engineer for the same reason. It's usually only one in five recordings that I truly like, and will be listened to again, occasionally. The other part is capturing a moment when a performer performs something unique in their show, such as a song that's NOT on a CD )or a cover), a variation of a studio cut, or a truly scintillating performance. Those are the real gems. To paraphrase a quote someone used to have on their signature here, referring I think to a Miles Davis live performance made into an album, "We taped it in case it didn't happen again. And it hasn't."
As far as screwing over the artists, the artists I tape probably make more off the ticket I buy to their show than any CD I might buy, and if I like them enough to tape them I probably have all their CDs already. I also only tape artists who allow it, so clearly they agree. I do agree with you that the scumbags who take traded songs, burn them to CD and sell them on ebay and elsewhere are scum, but it's the act of selling, not the act of taping that's reprehensible.
I think the majority here are driven by similar considerations, so please consider that before denigrating what we enjoy doing by the words you use to describe it.