The bricking has occurred to T-082 PSP's(
http://www.psp-hacks.com/images/ta82spot1.jpg). There was also said that there could be a risk in downgrading factory 2.6 firmwares, but I've only seen positive reports on these downgrades in forums.
For those who will downgrade it is important to read as much as you can about it, so you do it right all the way. You must use an older version of the GTA-game. I spent hours reading about the prosess, saw the tutorial video and checked in several forums before doing it.
And with Devhook I can run my GTA and SIMS 2 + UMD's without problems.