I've had the full size version for almost a year now and been an excellent gun for me. You can throw any kind of rounds you want into it (I buy reloads they sell at the range I go to quite frequently) and I've never had any problems with it ejecting shells or anything.
The compact version doesn't have the sexy "ergo grip" like the full-size has but it still has the interchangeable backstrap. The grip and the frame on the HK45C is basically the same as the P2000, another HK pistol I've owned that was very nice to shoot.
The only issue with the HK45 is finding a holster and getting tritium sights for it. HK came out with a plastic "SERPA" style holster for the full-size version but I don't think they made one for the compact. And I know the Blackhawk SERPA holster for the USP will fit the fullsize HK45 but I don't know what fits the C. Not too many people sell designated holsters for these guns yet. If you go into a gunstore and ask for one they'll just hand you one for a USP, a lot people haven't even heard of these pistols. I ended ordering a custom Mernickle leather holster that took 5 weeks to get made but it was well worth it.
And currently only Heinie makes night sights for these guns in their "Super 8" style which is a lot different than the three flat dots most sights have. Personally I'm waiting for Novak or Trijicon to come out with some before I install any on my gun but you might like that style of sight.
If you'd like more info there always
www.hkpro.com which has TONS of info on that gun.
have a good one