My 3420 is a PM605 (55cc). Yes it's heavy, and it's also wide which can get in the way sometimes. But I like it a lot, and consider it a quality machine. All of the parts and mechanisms work nicely and feel good. I like the design of it - they did things correctly, like putting the carb in a sealed box below the air filter which means your mixture doesn't change if the filter gets a bit clogged. The A/V works well.
They don't rev like newer saws but do have torque, and my 55cc pulls a 24" bar better than it has any right to. The oiler has enough flow for it too.
The main weak spots are the oilers and the ignition modules, and I've had both fail.
The oiler is pulse operated and really easy to get to, but the housing is complex inside and not entirely repairable. Both the manual and automatic oiler are in one assembly, but mostly only share the inlet and outlet. Do not use high pressure air on it - I may have killed my first pump that way. You have to do a fair amount of disassembly to replace the oil line in the tank if that is necessary, and it may be. It's really not hard to do, just kind of a PITA.
There's not much you can do about the ignition if that goes but to get another off of eBay or the like.
Also, clean and lubricate the recoil - I hear they can be problematic but mine has always been great, and has a good feel too.
I enjoy running mine and like the sound when it's working hard. It used a lot of fuel this year with that 24" bar buried in red oak, but it cut a lot of wood too.