Digging up an old thread here, but I finally found my solution to the "dull" HDMI output on the 622. I have a RP CRT (Sony KP-57WS510) which is fully calibrated by myself. For a very long time I have always used component inputs on the TV for Dish, HD DVD and Blu-Ray, all because the HDMI-to-DVI connection seemed dull on all devices compared to component and even after calibration the colors were not correct. And this was evident in the calibrations as well, the DVI input on my TV always seemed off.
Anyway, I was finally doing some more digging in the service menu and came upon a MTRX register (I've actually played around with it a long time ago), which controls how color is displayed, Rec 601 (SD) or rec 709 (HD). I had it set to "1" for HD just like all of my 1080i component inputs as this seemed like the logical correct setting. For the heck of it I switched it to "0" and the "HD pop" came back on DVI. I then threw on the colorimeter and sure enough, component and DVI inputs now were exactly the same.
So I'm not sure where the problem lies (what the 622 puts out or what my TV is expecting on this input) but when I set this register to "0" for SD colorspace they both seem to agree and I get the correct color.
So those of you with the "dull" issue, if you are using an HDMI-DVI connection it may have something to do with the handshaking going on and/or how your TV is expecting the data from the 622.