Greg from PS3-hacks.com has confirmed that the PS Downgrade from the PS Jailbreak crew is real! Here is what he had to say:

“I can personally tell you that PS Downgrade is the real deal. I’ll attempt a video later — just know I successfully downgraded my PS3 Slim running 3.50 to 3.41 a few moments ago. And so we’re clear: ps-downgrade.com is not a scam; they’re the real deal — and very helpful too. I bought my PS Downgrade update for $40 and although it took more than 48 hours, they still delivered; I understand that to be PS Jailbreak’s problem but lets not get into he said she said. After all the PS Jailbreak team did it again!

We have for you the modified 3.41 PUP, both Lv2diag.self files, and the PS Updater app (to update your PS Jailbreak with PS Downgrade). Instructions on all that below. I believe the FLA file (the PS Downgrade software) is specific to each PS Jailbreak device. But I’ve included mine anyway. Maybe someone can do something with it.

How to Downgrade your PS3 with PS Downgrade

1. Insert PS Jailbreak device that has been reprogrammed as PS Downgrade into your console
2. Turn on the console using the same boot method as PS Jailbreak: Press power then immediately press eject. Your console will turn on and PS Jailbreak will light up with red/green LEDs followed by green only, then the PS3 will turn off.
3. Turn on console to make sure you are in factory service mode. You will see a huge red box on the screen saying Factory Service Mode. Once confirmed please turn off console and remove PS Downgrade Dongle.
4. Program any blank USB mass storage device with 2 files:
      1. the modified 3.41 PUP
      2. Lv2Diag.self (rename Lv2diag.self.1)
These must be the only files on the USB key and must be placed in the main (root) directory.
5. Insert this USB mass storage device into the USB port to the right — the first USB port in from the right side if you’re facing the console. Turn the PS3 on and you will see black screen but the PS3 HDD light will flash.
6. Wait 3 minutes for the system to install the old firmware. Towards the end the power button on the console will start flashing green and then your console will power off.
7. Remove the USB key and turn on the console, you will still be in factory service mode. Please verify you have downgraded successfully to version 3.41.
8. (Optional) – If you wish to downgrade to any older firmware you can follow step 4, 5, 6 using any regular firmware PUP. (You do not need to use modified custom firmware now that you are on 3.41).
9. Insert USB key back into your PC, remove the PUP and Lv2Diag.self file, and copy only the other LV2Diag.self (rename Lv2diag.self.2) to the USB key.
10. Power on your console, after 10 seconds it will power off
11. Turn on your console again with no USB inserted and you will be out of factory service mode and back in retail mode with your chosen firmware version installed

With this you’re able to downgrade any PS3 running firmware 3.42 or 3.50 and “beyond” … I wonder if Sony has any plans on revising their hardware soon. I suspect this is similar to Pandora’s battery for the PSP, which ultimately forced Sony to release the TA088v3 closing off that backdoor.

If you just can’t wait and you already own a PS Jailbreak, or if you want to buy a PS Jailbreak too, then you do that and you downgrade your PS3; you can buy the standalone update or both PS Jailbreak and software
at ps-downgrade.com. Otherwise sit patient because you know this’ll be open sourced real soon.”
Source: PS3-hacks.com