Got the Beyerdynamic DT770 VB pads yesterday! The installation of the pads wasn't that difficult. I noticed an immediate difference in the comfort. The stock AKG velours are pretty comfortable, but with the Beyers, the opening for the ear is much larger. My ears no longer touch the sides like they used to. The Beyer pads are just a few millimeters taller, also.
I opted not to use the Beyer foam inserts. I did not notice any sonic differences between the Beyer foam and the stock foam.
Here are the AKG 240 MK II with the Beyer Pads installed:


My immediate impression was a slightly wider soundstage. The bass sounded punchier, but with slightly less impact. This is most likely due to the holes in these pads. The improvement in comfort is great, however, one of the things I like about these headphones is the bass, so I decided to mod the pads by covering the holes with some electrical tape.

You can see these holes with the pads installed:

The installation was super easy & only took about 10 minutes per side:

Now the bass is punchy with slightly better impact than with the stock AKG velours, & the headphones are way more comfortable!
I highly recommend this mod if you have big ears (like me) - the comfort improvement alone is worth it - even if you don't decide to do the tape mod. The best part is, it's 100 % reversible!
I plan on saving the AKG velours for my next purchase - some Fostex T50 rp.
Next up will be some cable rolling!