No experience w/ the 630 but did have a 770 (308 version). THE best hunting type rifle I've ever shot! The barrels on this series are absolutely great, polygonal cold hammer forged. Very accurate. The barrels don't heat up as quickly as most others w/ comparable taper and profile. The 770 (308) will give about 10 repedatively accurate shots before the bore heats up and effects accuracy.
Is it worth the price? Well, as with any discontinued HK, I'd say so. Parts are next to impossible to find and the resale value is iffy since these are not something the average person is familiar with.
If you do get one find a HK 05 mount for it, don't use the B-Square mount, they scar the hell out of the top of the receiver.
One other thing, the safety is the week point. I've seen several rifles in this series w/ failed safeties,and it is tough to fix.