I've been testing out Houdini 12.5 and Camtasia on OSX, and here are some things I've found. First, recording at the max speed of 30fps is just not doable. Houdini becomes extremely choppy. Using the "Medium" speed of 15fps allows for capture at 1280x800 and only slight hint of performance drop.
Next, the thing I noticed is that the loudness of the recorded clips may not be as loud as I hoped when played back on speakers. Many times I need to bump it up to max, and still it isn't too audible. And horrors, when new email arrives......
What I do right now is to set my microphone record levels at a decent level, so that it doesn't clip when speaking normally. Once in Camtasia's editing mode, I apply a Dynamic Processor (under Audio FX) onto the audio tracks that need them. The main control I tune is just the make up gain. At the defaults of 20 (db?), and I tweak that so as not to be too loud... you might want to read about dynamic range compression, and youtube has lots of audio compressor tutorials that will work with camtasia.
Export wise, I have observed that the default Share -> Export produces exports quite fast, but the file sizes tend to be humongous! For example, I had recorded a 4 minute clip, that Export spat out very fast, but at 90mb. Oooook. I then exported a full length clip at over an hour with the advanced export, and it was... 300mb. Eeeeyup.
The settings I used in export include using the H264 export at 15fps, multi-pass, with AAC audio. Oh, this is under "Export to Quicktime Movie".
At the time of this post, my system specs are:
2009 MBP, OSX 10.6.8. 2.4ghz cpu with 8gb ram.
Camtasia for Mac 2.3.0 (77283)