Yes, the MS400 should be a nice option. If Stihl made a truck, I would probably buy one.
As a note, STIHL would sub-contract manufacture to someone else; STIHL zero-turn mowers are nice--and
made by Ferris. STIHL provides excellent service on them
I hear.
The MS400 is being replaced with a 400.1, and to me it
looks like they're making a "more reasonable"
(i.e. "watered-down") saw--but I haven't seen one so don't count on that as gospel. If you can get a 2020 or later MS400 they're
(in my opinion) what to pick up due to the revised parts.
From the first video: Jens said the new MS400 is based on the previous MS400 but is a redesigned saw--basically the next evolution, not just an improvement. There's less rotating mass which is why it feels like a fuel-injected saw, the handles are redesigned for better balance and anti-vibration, heated handles will be available as an option.
Jens said the main benefit of the STIHL RAPID HEXA(tm) chain is consistent and easy sharpening for the average chainsaw user, and cutter longevity in dirty conditions (including roots) is improved.
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Regarding MS400 cutting ability
(I have an early one and wrench on a friend's 2023 which has several improvements), I find the anti-vibration a bit "springy" though got used to it and it is smooth. It does well for a mid-size saw in Central Wisconsin, which for the most part makes a great all-around saw as it's light enough for brush cutting with a small bar and powerful enough for pulling a 28" bar through most of what we have (or at least what I deal with). The fuel tank is a bit small so it's dry after 30 to 45 minutes of use, faster if constantly bucking "big" stuff (for Wisconsin).
Personally I usually use a smaller saw for limbing and larger for bucking over 14", but if someone were looking to own just one saw that "does it all" I think an MS400 would be a great choice as long as they had the upper body strength to run it comfortably. The auto-tune works great (there are no carb adjustment screws) in the hot/cold/100% humidity/dry conditions I've been in, so with that and HEXA chain it should be a versatile easy to maintain saw.