Performance seems pretty good in the new version. That was one of my big pet peeves with the old version was if you opened a folder with 1000 photos it would just hang for like 30 seconds to a minute doing stuff. Now it's pretty much instantaneous. The actual exporting is actually a bit slower. I did 10 photos in the old version and it took 1:57. The new version took 2:21. I'm not seeing any differences in image quality but it's possible it's there. One big bummer is nothing as far as settings seems to transfer between the two. Not even simple things like exposure or check marks. It's hard for me to want to switch unless they at least put in support for the 5D mark II. But I'm glad to see they're at least moving in the right direction. Just needs a little more work hopefully.
Canon allows you to keep both 4.0 and 3.x of DPP on the same machine means your hope may not come true. It seems that the DPP team is developing the 4.x for the current full frame cameras while updating the 3.x for the rest and old cameras, till you move your BODY up for the 4.x features.
Here's me hoping the Mk II will get supported in the next release
No way I'm getting a second Mk III body.
5D3, 5D2, Sony α6000, S90 | SY14 f/2.8, Ʃ20 f/1.8, 24 f/2.8, 35 f/2, Ʃ35 f/1.4A, 50 f/1.8 I, Ʃ50 f/1.4 EX, 100L Macro, 17-40L, 24-105L, 70-200 f/2.8L IS II, 1.4x II, 70-300L, 100-400L | E-mount: SY12 f/2, Ʃ19 & 30 f/2.8 EX DN, 16-70 ZA OSS, 55-210 OSS, Metabones SB | FT-QL, AE-1P | FD(n) & FL lenses