Had (not very good, unlike what everyone else seems to claim) experience of it twice in the last few months.
One frame was one I bought secondhand from someone (although it was a warranty replacement for him, so never been used). As I didn’t have proof of purchase, they flat out refused. Even after the guy at the Specialized concept store said he’d seen the same failure a few times before. Not really sure why I needed proof of purchase, thought the proof would be I had the frame there in my hands…
Second one was a frame I’d ridden for a few hundred miles. Crack in the chainstay (full suss Epic), so took it to my local concept store thinking they’d have a good relationship with Specialized. After 3 weeks and having to phone up a few times to find out what was going on, I got a replacement chainstay that’s the wrong colour and has marks looking like it’s been used. Took that so I have a bike to ride, but they’re supposedly trying to at least get hold of a new chainstay, but it still won’t be the right colour. That was a couple of weeks ago and haven’t heard any more, even phoned Specialized UK but was told they couldn’t help that week as the warranty guy was on holiday.
So overall, not great, contrary most responses you’ll probably get.