Well, my Mikunis are sold and gone, so for better or worse I'm sticking with these Lectrons. Overall still excellent, but also still fighting for a low smooth idle.
I ordered firmer slide return springs from Lectron, and that did help with getting a consistent throttle return. Stiffer in the the hand than the light springs I had, but not objectionable. Kevin says that the firmest springs are very firm indeed, and that the medium springs (which I now have) are okay for singles/twins, but probably too stiff for more than two carbs. Interesting things to keep in mind... Given the fairly common refrain about sticky slides at or near idle, I'd suggest that trying medium springs right from the get-go wouldn't be out of the question.
As for that idle... Kevin suggested I try 1/4 richer on the rod to "break up" the lean idle. I tried this for a couple days, and find that my plugs foul after about 20 miles of around-town driving! However, away from idle, everything else had even more pep than usual. I added a 1/4 turn to the powerjets, and the bike was highway champ until I ran out of gas... mileage down almost 20% with all the richening!
I'm tempted now to add idle air bleed screws to fine-tune the idle no matter what the rod setting. I've also gotten some slightly hotter plugs (NKG BPR6EIX) to see if I can control the off-idle fouling that way.
I'm still very optimistic about getting that last 2-3% of tune sorted; it took at least this long to get the Mikunis sorted. I'm building up a Honda XR600R, for which I'm seriously considering a 40mm Lectron... Like any carb, they take time to sort, but so far I'm still stoked on them.