Joonie released a newer version, psp isos now working, for those who don't wanna change fw again my Unofficial REBUG Updater v4.53~ Cobra Edition is forthcoming with Joonie's latest changes + remote play patch.
Should use 4.53.3U that was just mentioned by bitsbubba. Spoof to 4.60 works, and other bugs were also fixed by Joonie. So I would say that version is way more completed than the original 4.53.1 that was leaked/released.
I have been testing and seems everything is working. Except wireless controller sync problem with PS2 ISOs. But that is a minor bug. Just get a 10' USB cable, like I have.
This looks to be the best CFW/MFW release since Kmeaw. Just my 2 cents.