I ran a long thread on AS about the 661 "recall" (they were recalled in the EU but not here in NA) after they came out. They have since been re-designed (new P&C and intake boot, and a new coil). The ones in NA are all autotune, or what Stihl calls Mtronic. Meaning that a sensor adjusts the jets on the carb and the coil has variable timing. Mtronic comes on the 362, 261 and 441 as well. There is a non-Mtronic 661 but it is only available in Eastern Europe. I looked into getting one, but the cost was too high. Many people like the 661 and Mtronic saws, but I prefer to be able to tune my saws, so I am keeping my 660 and other non-Mtronic/autotune saws for now. The Husky 576 was autotune as well and they had a lot of problems with rolling that one out, but they later came out with a tuneable one.
The issue with my list of saws is that with the exception of the 550xp and the 576xp, all the saws are no longer sold new in NA. The main reasons are smog, strato/xTorq air injection and autotune/Mtronic, but in the case of the newer 372 the vibration also went way up. I think that the 461 is the better Stihl saw, though it is AV rubber mounted and not spring mounted. It is not Mtronic and not classic strato. Supposedly the new version is coming out soon. Supposedly. The Husky 372 replacement prototypes have been tested in the field for over 3 years now, and no word on that ever being released. Its in development though.
So I would add the MS461 to my list above.