Desktop Linux is unstable.Nonsense.
[joe@delilah installer]$ uptime
17:21:39 up 16 days, 9:17, 9 users, load average: 0.40, 0.26, 0.24
And that was a reboot because I had to run Windows for something. I'd gone probably two months without rebooting before that.
Linux, desktop or otherwise, is stable as hell. I stay logged in for months at a time without even thinking about it.
While it doesn't crash often, it does sometimes, and I feel that one crash is too many.
I've seen Mac OS X crash more often in the past two years (the time since a good friend started having a Mac laptop around me enough that I'd have an opportunity to see it crash) than I've seen Linux crash, and I don't even own a Mac (while I have at least one Linux system running every waking moment). In my experience Mac OS X is an order of magnitude less stable than Linux. It would have to be for me to have seen a dozen crashes over two years from a system that I see working for maybe a few hours every week on average, vs. my Linux boxes that I see running 80 or 100 hours every week. And, it's a well-maintained Mac, serviced by Google's Tech Stop.
Multiple displays are wonky.
This one I'll concur on...sort of. It was pretty bad until a couple of years ago. And, it's still bad on some hardware. But, on the best supported video cards, it works very well and without hassle. You do have to be careful about hardware...but Linux probably has more supported hardware these days than Mac OS X or Windows Vista (though very new stuff often doesn't have good drivers yet).
Flash still doesn't work properly.
I haven't had problems with Flash in years. There is the problem of running Flash on a 64 bit install of Linux...but if you use a 32 bit Firefox build, Flash works fine (I'm running on a 64 bit system, and I have no complaints about Flash). This is an issue of the vendor not providing a working 64 bit build--nothing to do with Linux. And there are easy workarounds.
I'm not downmodding, I just don't think your arguments are accurate. The cohesive UI argument is pretty much the only thing I will actually completely concur on. But, the cost of getting a cohesive UI is to give up a cohesive and sane command line (using Mac OS X on the command line makes me very angry, and I have a dozen terminals open at all times, so I would be very angry indeed working on a Mac all the time), not to mention all the other third party tools you have to give up to retain cohesiveness...I just don't see how that's a good trade.