Everything said so far is true or can be, though I always use flint bevel down on that lock and never saw one torch a flint... My older cast springs were tired after thousands of shots, but forged spring upgrade fixed that. Newer ones come with forged springs. I don't know how many shots, but I've burned out 2 or 3 touchhole liners so far and could use another. The frizzen was a touch too hard on mine,also, but I drew the temper back. Mechanically, I don't see any major issues with the one I got, and the more recent ones seem finished and assembled to a higher quality in general compared to the past. And, I think they have made some improvements in metallurgy on the frizzen as well. It is a very fast medium/large lock when set up and configured correctly.
The chamber's late ketland is not as nice in appearance options, but gets rave reviews from me and others in terms of speed, reliability, and build quality. I think it is closer to typical British export lock used in colonies, but not always the right choice aesthetically or even functionally either.
I would use durrs egg again if it best fit a project, but I would allow time for inspection/tuning, or seriously consider Roller(TM Bob Roller) version if that's an option.