MX worked fine for me before the switch up to 10.3, just wasn't happy after that. Since it came out a 2 years or so before 10.3 can't really complain that much with the few small issues there. I do wish Macromedia would get their "choice word" together and actually debug/optimize their apps before the general release though. I get the feeling they just don't try hard enough, as even the win version are slow in their own right.
Maybe Adobe's new 'methods' have knocked some sense into them. Before CS GoLive wasn't anywhere near the level of Dreamweaver, it's caught up now and maybe surpassed on some things though I still think DW (04) is a better app for the money. I would love to see someone (Macromedia) create a BBEdit style one on steroids. Junk the visual mode and give us a fast, efficient, code view without alot of the extra junk.
Why do updates when they know your only option is to pay for an upgrade to fix thos issues. Sucks but it's the way big business goes.