I never had a problem that needed onsite specialty. I was the onsite help.
While you didn't, this is pretty standard fair for server products. All the Dells in the rack next to the XServes could have a Dell technician on site within 24 hours. Meantime we were sending entire RAID boxes to Apple via shipping.
Their shipping was like overnight for any parts you needed and I had spare kits as well. Server blows up just grab a logic board, yada yada.
Which works great when you know what's wrong, not so much if you need diagnosis.
Most large enterprise business' only need 24Hr phone or chat. Nothing was ever not resolved. They send you code, binary patches, whatever. I had only 10 Xserves going at any one time. But they anchored the phenomenal client growth over the last few years.
This would be great if they could repair servers over the phone. We had the highest levels of their phone support and still could not get our issues resolved.
10.5.8 is pretty good still. Using it all over the place. Adobe had a hand in killing OS X as a major player what with ACL, SMB, AFP, POSIX changes every freakin release. Apple went one way and Adobe went the other. Respected permissions one day not the next. If a server OS can't get permissions right I don't see the point. But Adobe really needed to respect ACL's over AFP.
We had 10.5.8 back when I worked there. XServe RAID + ACLs = continued panics with data loss. Totally unreliable.
If you're doing very basic serving, yeah, it works ok. If you're doing anything complicated (i.e. using hardware and software that they sold at the time in a way they advertised it), it was a mess.
We called up our Apple reps and threatened to trash our XServes and switch to Windows many times. It had nothing to do with applications, it had everything to do with OS X Server being horrible at anything but just being a basic AFP server.
While I wish Apple had kept the XServe, it's totally understandable why it was killed.