Well, I will give it a go.
First you must use the Native X setting to get the full potential out of the upgrade.
If you have a PW Transport and use the I2S output to the PW DAC you will get a CD player that will beat all but the best and still rival them.
The fact that all inputs have the Lens Tech makes this a worthwhile investment IMHO. It improves the sound for all inputs.
You will hear a more refined sound. Better dynamics, sound stage, more transparent, less digital and I think more musical.
Will it be night and day? I guess it depends on your system.
I felt it was worth the upgrade. Keep in mind it will need to be burned in again as you have a new board.
But there are other things to consider.
PS Audio is working on the next upgrade. When? Anybodies guess. I would say no earlier then end of this year. No later then end of summer of 2014.
But when that happens you might pay more to upgrade on a MKI vs a MKII I would expect.
Then there is all the other DACs that have and will be coming out in the next few months in the $4-5,000 price range.
If it cost you to upgrade now about $8-1,000 and then to the MKIII another of the same you would be around $1,600 to $2,000. A lot less then what you would have to spend for a new DAC that most do not offer a hardware upgrade path.
I would expect the same worthwhile upgrade in sound from the PS Audio MKIII when it come out.
What ever you decide good luck.