Just various little things that are off - general laggier response than sense rom, a text message along with every voicemail, odd power management with the screen not turning on when it's supposed to, lack of FM radio, etc. All little niggling things that I've been willing to put up with for an immature project with a solid foundation, with the expectation that it will mature into something greater.
Are you sure you're using the actual official CM release, or just an unofficial port? I have no problems on my Galaxy S2 (T-Mobile even!) even remotely similar to yours.