The Grace Design V2, V3, Graham Patten DMIC-20, DMIC-24 and Denecke AD-20 are all instrumentation based microphone pre-amps. The instrumentation amp based pre-amps have been getting more popular over the years, because the instrumentation based microphone pre-amps require less discrete circuitry than op-amp based pre-amps and sound pretty darn good.
I started getting interested in these amps after reading this:
http://www.audiomasterclass.com/arc.cfm?a=giant-killing-$5-mic-preamp-its-secrets-revealed
An electronics hobbiest can build one of these pre-amps fairly cheap. Again, read the $5 mic Preamp article.
For me, with the parts I already have, plus the cheap batteries and the already designed, layed out, stuffed and tested circuit that Jon sells. I built a small, efficient very clean, 48v phantom powered pre-amp to run line-in to any of my recorders.
The unknown element is how it sounds... I know that it will be clean and efficient from my experience using the various other pre-amps based on the instrumentation amps.
I enjoy tinkering with electronics and view it as a fun thing to do. I anticipate that the pay-off will be a small, very clean, low noise, relatively cheap microphone pre-amp.
I plan to post recordings made with this pre-amp and report back my experiences good and bad. After building it, I have a good feeling about it.
edited for spelling...