I tried a roll this evening at the rated speed. Exposures were both by natural light and by electronic flash.
There haven't been any times published as yet for Microdol-X, so I took a chance and kinda half guessed a starting time. Based on the published time of 10 minutes in D-76, I used my convoluted thought processes to come up with a magic time of 16.5 minutes in Microdol-X 1:3 @ 68F. Don't ask, I just did...
From my initial examination (the negs are still drying), it looks like I got a pretty damn close, if not the correct, time for Pro 100. I will try another roll sometime this weekend and give it about 10% more time, just to see if I squeak out a little more shadow detail.
One thing I find rather interesting is the film base of this stuff, it has a very different feel to it, almost like a heavy cellophane. It has a look far different from the offerings of the Great Yellow Father, not like THAT is a bad thing!