I've had two of these low cost mk219s around for several years.  They're not bad and I've had good luck with them on quite a few projects.   I've used them as Drum Room Mics, Floor Tom, Acoustic Guitar, Background Vocal, etc.

I've been interested in what Oktavamod/MJE could do for these for a while.  For $280 they pretty much gut the thing and re-build it with a new capsule and headbasket and "premium" electronics on the circuit board.   

 In October, I decided to get one of them done so I could compare.  MJE is very offical - when you buy the mod, they email you with a "mod date" and a return date.  You have to get the mic to them by the mod date and the idea is that they will ship it back by the return date.   Well that came and went.   MJE is very busy these days with various branded products now plus Hurricane Sandy knocked them out for a couple days.   Eventually it came back (signature required so note to self: next time have it shipped to work).   Here is what it looks like next to the unmodified version

Unmodified Oktava and the MJE on the right

 

Here's a higher quality photo.  Click to magnify:

 Close-up

Listen Up

So what does it sound like compared to the unmodified one.

Here is a comparison of a recording of my 6 String Acoustic guitar with the stock mk219 and the same section with the MJE modified mic.  These are 16 Bit/44.1 wav files (sorry).

6str-acu-mk219-stock.wav

6str-acu-mk219-mje.wav