What GL said pretty much hits the hammer on the nail. Errr.. the other way around.
Anyways there are actually two different DivX codecs; low-motion and fast-motion. The fast motion is absolutely horrible at everything, including fast-motion scenes. The low-motion is generally decent for fast-motion scenes, and wonderful for low-motion scenes, as long as you don't resize from native resolution (704x480 or something), and use at least 700kbps bitrate.
And with the latest version of Flask, you will most likely get audio and video out of sync if you are encoding audio to MP3. If you are encoding Audio to PCM Wave format, it's generally okay. But then you have to mess around with VirtualDub after that, to compress the audio to WMA or MP3, since PCM Wave is ridiculously bloated (130KB/sec or something like that). Anyways, messing around with DVD ripping and DivX encoding can really take up lots of your hard drive space, I'll give you that much.
BTW: So far I don't know of any way you can use those various hardware accelerators (such as Hollywood+, or the motion-compensation features on GeForce and other chips) to accelerate DivX/MS MPEG-4.... it just isn't possible. MPEG-2 is not equal to MPEG-4.