A friend of a friend makes ScreenFlick and it works well: http://www.araelium.com/screenflick/ Before that I used SnagIt, and before that I used Screenium, until I started having issues withit on the latest OSX.
I bought Screenflick (http://www.araelium.com/screenflick) for OS X. $29 but works really well. I teach a programming course so used it to capture my slides/text editor, as well as my mic input. Works great.
I'll try it out tomorrow morning, glad to help out a fellow iOS developer!
Otherwise, check out Screenflick for recording the videos. It helps me a ton during my own work with XCode and works really well with the iOS device simulator.
I used ScreenFlick to create the screencast and it's got the "display keypresses" feature built in. It's really quite a nice app -- the only thing missing is that you can't edit the screencast after you record it at all.
I've been looking into this myself. I haven't tried this yet, so I can't say from experience but this looks like an alright solution that's not too expensive.
http://www.araelium.com/screenflick/
If I end up trying it I'll let you know if it's worth the money or not.
Edit: Just gave the unregistered version a go. Pretty happy with the quality. I wasn't playing the most taxing game (Hearthstone) but it was able to record in 720p, 30 fps consistently with a pretty reasonable filesize (~2GB for 10 mins). If you're not playing in full screen it can be a bit annoying as you have to set the capture area of the screen when you hit record. The main issue I have is that the mic isn't recorded to a separate track or file. I'll probably just record the mic in Audacity to get around this though.
Ultra late answer, but quicktime is sure to lag the game quite a lot :/
I've tried pretty much all screen recorders available (haven't bought them all, of course: I pirated since it was just for testing and have deleted them since) and I can say that the best one is Screenflick;. This one works wonders. I've tried Screenflow, Camtasia, as well as some others, and this one is the one that causes the less FPS losses. I am able to get around 45-50 FPS when not recording, and when recording it comes down to 25-30. Pretty good if you ask me.
So I dunno, OP may give it a try. Note that the Mac I tested this on is from late 2009, and it's not a very powerful one :)
Screenflick works pretty good, but it's not as feature rich (or as expensive) as Screenflow. you can't edit a recording with it, for instance; you need something else for that. I use Avidemux.