Has anybody used an analog mic to USB adapter and can comment how they work- if at all ???
Yes, I use several different. But as always, you more or less get what you pay for. Prices has moved down considerably the last few years, but for top quality you need to pay. The cost is partly due to needing analog components where the price has not moved down along with the digital revolution.
Only one example: a unit I own and like is the RME Babyface. Retail lists it at $799. Quite a chunk of money, agreed, but the sound quality is well above the audio input of any Mac which I request as I use it to record symphony orchestras. This is professional quality, useable also in a commercial studio setting, although a "real" studio tends to go even higher in price. It fits my usage as I can connect two microphones for stereo recording and feed them 48V phantom power (which my mics require), and it lives most days in my setup doubling as monitor controller. But that is my situation.
http://www.sweetwater.com/store/detail/Babyface
There are literally hundreds of USB interfaces on the market, priced from a few tens of dollars up to 6000 dollars and more. I find it hard to recommend any one specifically as your requirements on sound quality probably are different from mine.
You should be able to get a working unit for less than $100, but how much less is a bit difficult to say. By working I mean that it runs well with the mac without hiccups and that it has reasonably good frequency range and reasonably low self noise. Even low priced units today offer about 90dB signal to noise ratio, and with careful use this is about what you get from most CD-s ( maximum S/N ratio of a CD is a few dB-s more, we could have a very long discussion about exact figurers here, but lets not do that ). It is about the kind of quality you get from the built-in sound inputs on macs. Some units allows you to connect microphones directly without losing quality, other units require external preamps for mic inputs or loses in sound quality. It all depends as people say.
Perhaps others can chime in with their experiences.
// Gunnar