I just found a blog post by an acquaintance of mine (Ted), comparing Apple's Aperture with Adobe's Lightroom. It's well written, and I think I agree with everything he says in there (well, some things I hadn't tried doing, but everything I've tried...)
I, like him, am frustrated with the lack of an update for Aperture lately. I really liked it for a while there, and I miss it, now that I'm predominantly using Lightroom. And yet, that's the situation: I'm predominantly using Lightroom, because of issues with performance in general, and also, something Ted doesn't mention (because I presume he hasn't tried it), the way that Aperture utterly fails to behave properly with a project whose RAW files are on an NFS-mounted drive, once you quit Aperture. There's a way to work around it ("reconnect" the masters), but boy is it a pain. Those files are in the same place they were last time, and the drive is online and mounted, so very frustrating for Aperture to claim they're missing. Not to mention slow to reconnect a large number of them.
So, here's hoping Apple is still working on this -- both because I want Aperture to improve again, and I want the pressure of continued competition to make both options better.
Alas, for a variety of reasons, the notion of writing my own competitor is unlikely to ever happen... it's very tempting, though. I think the world could have a lot better than either of those programs, in certain ways.
If anyone wants to start an open source project, though, I'd be glad to contribute some time and ideas, and likely code, to the effort.