This has been mentioned briefly in other threads, but figured I'd post one with the subject in the topic and actually review one. I also want to state I have no affiliation with this company, this is an unbiased review.
So I've been working on a black knight on and off for probably the last 2 years now. Tried a $200 used rottendog board, still had issues (ended up selling to a friend, who needed to send it in for repair). Restored the playfield and cabinet, ended up putting the original board back in and had a tech fix some switch issues. Played it for a while, wasn't happy the lighting to alert you that you got magnasave wasn't working. So I tried replacing the diodes and caps on the trace that controls it, didn't fix it. Then I tried replacing the PIA chip, ended up doing more harm than good, then the traces lifted. So then I bought what was supposed to be a refurbished driverboard off ebay for $100. Attract mode was back, but wouldn't start a game (switch matrixes were effed up).
So now I'm really into this, 2 driverboards toasted and a rottendog. It's been months since I touched it because I don't want to dump any more money into it. So then last week I have some leftover paypal money, so I decide to take a gamble on pinballpcb.com for a new driverboard. They seem to be reputable, and although 2 boards would cost you more than one rottendog board ($375 combo vs $280), the boards look to be built better and closer to the original (while updating to modern components). Popped it in, game starts, all lights work.. But sound isn't work (not related, I had flakey sound issues before this started). Also the board itself has really nice LED strips that illuminate when a gate (lamp or solenoid) is fired, so it's good for troubleshooting too.
The board also comes with a great manual with a binder, has troubleshooting inside and full schematics (which is nice in case you do have issues).
Also note, when I had the tech over, he wouldn't touch the rottendog board. I've also contacted the coin-op cauldron, and he doesn't work on them.