Mike, these things generally sound bad when used with many common radios. I think it may be partly an issue with the frequency response of the radio.
A throat mic (or those awful ones that put the mic in your ear canal) will lose much of the higher audio frequencies essential to understanding consonants in speech. If the radio does not sharply cut low frequencies to balance this effect, you sound like you're talking through a pillow.
Engine and wind noise both have lots of low-frequency energy, and your neck and chest make a great resonator. Limiting the low-frequency response of the radio's mic input would help there, too.
The ear canal mics are especially bad at boosting the frequencies at which your head resonates, making it sound like your talking through a paper-towel tube.
The quick, dirty way to cut lows is to insert a series capacitor in the "hot" lead of the mic audio, but finding the correct value requires knowing the impedances of the mic input and the mic itself. Also, a series capacitor will block DC, so if it's required as part of your push-to-talk scheme, it will create a problem.
Modifying the radio's internals is often the most elegant way to alter frequency response, but it's (a) difficult with the new surface-mount components, (b) risky to the radio's reliability and resale value, and (c) illegal in a certificated aircraft, and could cause illegal out-of-spec transmitter operation in ANY aircraft. In short, this should be designed, not "hacked."
These alternative mic types are becoming more popular as the use of MP3 players, digital cellphones and bluetooth earphone/mic sets lowers our expectations for audio quality. This stuff matters when you fly. There may come a time your life depends on being heard and understood clearly. If it means a slightly less convenient mic that's located in front of your mouth, it's worth it, IMHO.
Most people test mics by going flying and getting reports from other pilots. They'll usually be overly polite, when in reality your intelligibility is severely compromised. You should go flying, and leave a recorder fed by a radio on the ground, so you can listen to your own audio when you get back. If you do, you'll probably be shocked at how bad these things sound on most radios. If you conduct an A/B test with a properly positioned boom mic, you'll probably hear so much difference you won't want to fly with a compromise.
As someone who deals with audio professionally, I'm discouraged at how new technology is not used to improve communications effectiveness. The state of the art seems to have peaked sometime in the late 1970s...since then, it's been all about cutting costs, bandwidth and physical size.