Ah, lake Chelan mackinaws. Anton Jones is this site's guide expert for lake Chelan. You can click on his link at the lake Chelan section and he will be happy to answer questions.

I can tell you what he has told me. The Derby: last year the amount of chinook caught was so pathetic that the Derby folks decided to just do macks. Seems the chinook fishery is just about toast. Lake trout NO Limit: yup - WDFW has decided that the TROPHY lake trout fishery on lake Chelan is not what they want on the lake. They want to fish out the macks (like that's going to happen) and instead focus on cutthroat, rainbow, and silvers. Seems they think lake trout are too hard for the average angler to catch and they want to have fish that anyone can catch. Plus, they want to reintroduce the original species which lakers aren't. Haven't heard about them removing the non-native dam at the end of the lake...
Macks taste great smoked. Baked they are rather mild in my opinion, but not bad.
Anton sent in some more reports of great fishing and some larger fish being caught - 11 and 13 pounders. Plus a whole lot of 3-5 pound fish being caught. It's a deep water downrigger fishery that is red hot and has been for months.