I'm using DWMX for several months now on 10.2, and never had a problem. It is at times slow, and it has some bugs, but seems stable to me. What I don't like is that when I switch from DW to IE, and want to go back, I have to click the icon in the dock, or have to click a DW-window, the IE again, and then DW again to bring the DW-window to the front. That's annoying.
I've been using MX in OSX, and while I've had some problems with MX, crashing isn't one of them.
some other complaints if your curious ? detailed tags in site files view stay on screen even when another application is brought to the front. I have to go back to DW and roll over it again to make them go away. ? ftp reacts very slowly (much, much snappier in 9) ? sites previously created with DW4 templates break when the template is edited in MX. I would love to find a solution to this problem. I thought I had it at one time, but I'm still having this issue.