There are endless little dicussions like this all over the Internet about Dreamweaver MX and every other piece of technology you could think of, including ones that you love... ones that I think are great.
It is a problem that they are fractured and scattered all of the place, in places Macromedia will never find. They've found this one which is good, O'Reilly.com is a 'well known place' obviously but still this is one random article. Even if you stuck to just major mainstream periodicals and publisher websites you would find dozens of Dreamweaver reviews and almost as many discussions.
What's my point. If you have an issue with a Macromedia problem, the best place to take it is Macromedia. If everyone did that they would know exactly where they stand with Mac users and every other category of customer. Macromedia knows how many Dreamweaver licenses Macromedia has sold to what platforms, what version and when. If a significant # of users start complaining (to Macromedia) then they'll certainly know they have a problem - whether a technical problem, image problem or whatever.
Macromedia has openly acknowledged this issue here x2. I'm not saying that the discussion isn't helpful... just the dog-pile style ranting. New comments have been added in since my post that are helpful in my opinion. They contribute new information about these performance issues. New "yeah Macromedia sucks bad..." comments aren't necessary, they've been made here already.
Hey, I'm just saying that I've been involved in IT for a long time and it is rare for a company to openly fess up to performance issues in a shipping product. I'm thankful for that as a user. I don't think it makes sense to slap it away.
I'm sure that the best way for you to complain to Macromedia about a product is to take the issue to Macromedia.
In the interest of adding some helpful info... here is a link to Macromedia's support site that talks about "emerging issues" with Dreamweaver MX on Mac OS X including this one.
They've also posted a performance survey here. Everyone who has Macromedia Dreamweaver MX would do themselves nd everyone else using the product and Macromedia a favor by investng the time to take the survey
(I think this will work if not then there is a link to the survey on the emerging issues page above).
I'm in favor of Mac OS X being a strong platform. That requires great applications running great on Mac OS X. As users we should be concerned about doing everything we can to help developers build support and maintain great Mac applications.