Quoted from PinMonk:
There was also a thread recently with a massively warped playfield that Stern would not replace. They're not always great.
In general, Stern and JJP both have their support wins and fails. Having dealt with both on a wide variety of NIB pin issues, I would say they are on balance very similar for support - good.
That thread where the guy picked up a used Metallica where the cabinet may have been out of square? It wasn't clear how old that game was or what had happened to it or that he even tried to get Stern to replace that. I also have seen pictures of scratched DP play fields that look like they happened while trying to bend a ball guide that was still attached to the playfield. I've also seen dozens of threads complaining about playfield dimpling or cratering and I think it would be ridiculous to replace play fields for that, but not everyone agrees.
I agree that people have reported good and bad customer support experiences with every manufacturer. That said Stern has replaced a lot of play fields that had issues. Personally I can say everyone I know who had a reasonable issue with a Stern playfield got a populated playfield swap or a new unpopulated playfield if that was their preference. I realize that they didn't replace it for every owner that wanted one. That sucks for them I'm sure, but not the focus of this thread.
I feel like a lot of posts in this thread are stuff - like X manufacture refused to do Y implying that JJP has no obligation to address this issue either. I disagree. There are multiple examples in this thread of people with JJP POTC that have not gotten an appropriate solution.