Thinking about getting one....
....does this unit allow for volume adjustment on each channel independently of the other?
Unfortunately, no it doesn't.
If you need independent gain my ugly has that feature and its the same price. But you must use some form of 1k tone to calibrate your mics so that you have an even sound from left to right. This is the most important thing when using a preamp that has independent controls so that you can get the most from your recordings. Anyone running a preamp that has independent controls of left and right that are continuous Not detected should be using this simple method.
Mount both mics on axis to a speaker shut off the other speaker of the stereo set put a 1k tone though your speakers place the mics no more then 1m away from the speakers and place both mics as close as possible to each other.
Then record a wav file and look at it in a real audio program and measure the average level between left and right. This will give you your difference to add to the signal in post or in the field you must then calibrate your preamp so it adds this difference always that way your stereo image will be perfect. Nobody does this I wonder why because this can have such a huge impact on the sound of your recordings its not funny. Relying on your R09s vu meter will not give you the information you need to balance out your recordings perfectly. If your running my mics you only have to adjust gain because you know your mics are matched. The method I use is more advanced then this but this is the basics of how I match my capsules. When I match I match for amplitude at 1k frequency response from 20hz to 20k and distortion percentage. So both mics exhibit the same distortion characteristics and frequency response and absolute sensitivity at 1k I use an acoustic coupler to do this so there is no error with placement.