5.50 Prometheus, newest CFW created by Liquidzigong (of earlier Prometheus ISO patch fame) released today, supposedly allows for playing all recently released 6.20 games, including titles like Metal Gear Solid: Peace Walker or Kingdom Hearts: Birth By Sleep without patching. Download link below.
I've only just installed it myself and it's more of a patch for 5.50 GEN D-3 than a full blown CFW.
It flashes 5 prxes, all into flash0:/kd/ folder, and those files are moon.prx, peagasus.prx, prometheus_lite.prx and vshctrl.prx. Everything seems to work fine, sadly I don't have any 6.20 UMD's I could use to try out it's main feature.
5.03 Prometheus for PSP 2000 - TA088v3 and PSP 3000 users at