Has anyone had any success flyfishing for smallmouth in either Lake Washington or Lake Sammamish?

Yes -
Fished post-spawn with WF7 full sinking lines (usually a type 4 or 5 sink rate). 9 foot leader with 2X or 3X tippets. Best flies were woolly buggers tied with a full marabou feather for the the tail. My best colors were black with purple body or brown with olive body with an overall fly length of 3 to 4 inches. Smolt streamers (especially in Sammamish) and scuplins are also good. Found that weed-guards were not necessary for most smallmouth water.

Fished mostly on the outer edges of the feeding flats with the boat in 20-25 feet of water and casting in 8 to 10 feet of water. Really helped to have a boat rigged like a bass boat. My catch rates with flies were a little less than with gear. One of the side benefits of chasing smallies were the ocassional really nice cutthroat.

Tight lines
Smalma