Well, I personally have no other issues with D that I would call 'critical mistakes', this is it... and it is a pretty big one. From a performance point of view, it's very dangerous, and I've also illustrated a whole bunch of other reasons why I think it's a mistake irrespective of performance. Also Andrej's recent point was interesting.

Any other gripes I have are really just incomplete features, like rvalue -> ref (or scope's incomplete implementation as I've always imagined it), allocations where they don't need to be, better gc control, and general lack of consideration for other architectures. I can see movement on all those issues, they'll come around when they've finished baking.

Meanwhile, lots of things that were missing/buggy have been fixed in the last year, D is feeling loads more solid recently, at least to me. I've been able to do most things I need to do with relatively little friction.