I know this is an OLD thread, so forgive me for bumping it, but seeing as how this saw is still in production means there might still be relevance here for prospective buyers.
I bought one of these about a 12-18 months ago. My used 350 died and 346's in this region are like unicorns. I had already purchased a 562 and needed something lightweight and good for small stuff (mostly tan oak/doug fir, some madrone, the occasional live oak).
As others have said, if you take this saw for what it is, it's a pretty nice machine. If you are trying to compare it to other saws, it's not going to measure up. It also largely depends on what you are doing with it. We work in dense forest, mostly, meaning lots of slash-cutting trees out of canopies. I've pushed this little saw to its limits slashing 5-7" tan oak, often having to make a slight cut at the base of the slash to ensure no barber-chairing or peeling, as the saw often cannot make it through the cut before the tree comes loose otherwise. While not essential (not timber) it's mostly for my own safety and peace of mind. As far as using it for falling small trees with face-cuts, I've had no problems keeping up with the cut in 12-16" hardwood, and upwards of 18" soft-wood. Keep in mind, these were even-weight trees with little to no lean. I would not trust this saw up against any kind of head-leaner or more difficult situation.
While I prefer the 16" bar for balance and motor efficiency, I have also pushed this saw with a 20" bar, working on a second chain now after taking the cutters all the way down to the line, full comp/semi-chisel.
It took about 20 hours to really break in. At first I was thoroughly disappointed with this saw aside from the light-weight aspect. Once I stopped comparing it to the 350/346 and learned to not push it like it was one, things changed for the better.
I still DO NOT like the mesh air filter. It gets too dirty too quickly compared to a fiber-filter. I work largely in wet conditions and during the rainy season, so gas-baths aren't always an option during lunch on a cloudy or drizzly day. This is one area Husqy needs to improve. The only other real issue that I've found with it, and this is likely exclusive to mine, as my dealer hasn't had anyone else make this complaint, is that the case clogs up with chips around the slot near the brake-ring. I've had to repeatedly take a crescent wrench and pry the flap back because it seems to get forced down and cover the hole enough to cause a back up. A couple times this has happened IMMEDIATELY after cleaning the clutch-case thoroughly.
My advice to gain full appreciation for this saw is 1) religiously clean the air filter, moreso than other saws I've used, 2) religiously clean and inspect the clutch cover, 3) don't expect it to be something it's not (or modify it to make it what you do want.)
My only other issue with this saw was the price. Way too expensive for what you get, especially compared to the 550, but then again, they are not meant to be the same saw. These saws haven't sold like hotcakes, so my dealer gave me a break on the price, but even then the cost:benefit ratio is steep. Either Husqy should drop the price $50-100, or find a way to add a twinge more power to the motor and provide a more durable/hardy air filter. The other disappointment was the lack of a dog. I often find myself having to pay attention to not sticking the case up against the wood, as this also impedes the chip-flow from the tiny exit at the front of the case.
I'm giving strong consideration to paying for some adjustments to this saw, but as I've just acquired a second 562 (half-wrap, single dog, 20" 3/8 bar) to replace the 543 as my main saw (the other 562 is a falling-saw, full wrap, 24" and 28" when rarely needed), I can't justify it yet, though possibly over the summer when the 543 will be stowed away. Mweba has certainly re-piqued my interest in going that route.
TL;dr
Don't judge this saw without trying it post-break-in and don't expect it to be similar to its predecessors. You might actually be relatively pleased with this saw.
Cheers