Our distributor who services most of the mid-west has 150 660's left in the warehouse before we get the 661, can't wait until they are gone, we have logger's waiting on the 661.
According to our distributor Stihl has never licensed Husky AT technology, Stihl was the first to use it using one solenoid on the MS 280 platform and then going to two solenoids on the current CM platforms, that is why Stihl has had no issues with the CM's as compared to Huskies learning curve with the AT. With Zama being the primary carb supplier today, Stihl gets to see the performance parameters of their competitors platforms way before they hit the market, since Stihl owns Zama.
The 1 series as in the new 251/271/291/461 all show great improvement over their previous platforms, can't wait to get my hands on a 661. Loggers who have bought the 461 say it cuts right with the old 650's. In a conversation with a local Husky dealer who comes in to buy Stihl repair parts stated in the last Husky tech class, held within the last month Husky stated they have finally fleshed out all the issues with the AT platform, I can't speak for AT's but we have yet to see one M-tronic saw come in with any issues.
We have hooked a couple up to run diagnostic's on them just for the practice, which is e-z pz to do, and you can do a manual reset on the M-tronics as well.