Well done.
I try not to critique hard because I can't make a flash game myself, but I looked at the other reviews and you actually seemed to appreciate honest feedback, that's cool. You mentioned you preferred your own music. Me too, I almost always end up turning off the music in favour of my own after a while. Not always though, I like having options for sound, really it shouldn't matter in the end but a sense of control over stupid details feels nice. Pick some good music, maybe a variety of song loops that a person could pick from, and a mute function for when they get bored of your selection. Sound effects might be a good idea but I could really see clanging swords and some generic death sound getting on my nerves quickly considering how quickly some of the fights go. I'd leave it out but it might make people happier if they were there and also equipped with a mute function.
The graphics? Loved them. People are huge fans of options though and for some reason aquiring meaningless achievments. You could probably very easily reward people with options of different lookings swords by reaching required levels of difficulty or some such thing. Maybe able to change the colour of your circle or pick little symbols or something. Nothing too fancy, just there for the hell of it. Think of parsley, it doesn't affect your meal one little bit but it just seems like you should pay more if you get some.
Changing the look of the level every couple of levels would be cool too, once again doesn't affect the gameplay.
Now for the gameplay: I liked it, don't change it. At first I was annoyed at having the game pause after every death, but after a couple rounds I realized it was the only sane way to go about it. The self adjusting AI was cool, although sometimes i would get on a really good run and then lose six in a row but no big deal, losing is part of the game.
So yeah, well done, I hope you're well fed.