OK I am impressed with the saw, it started without any problems right out of the box(after I fueled it) this is nice when you take a new one off the rack and prep it in front of the customer. I hate having to dig limiter caps off to get the thing to run with the customer there. It seems to have plenty of adjustment for the carb adjusting screws. It runs at its advertised 14,500 rpm. As I said earlier it has very good vibration dampening. I like the convenience features, outboard sprocket, side tension, easy off cover and air filter. I don't care for the cable throttle linkage they never do seem to loosen up. I ordered mine in with .325 chain figuring it is a runner and not a lugger (I'm the guy that loves .404, so this took some faith on my part) the factory chain is junk, big suprise. I was running it in some bone dry oak off the woodpile did real well until the chain lost it's edge.
Needs a compression relief, I could start it my father couldn't. I had him start a warmed up xl12 no problem. Now get this he drug out his 041 Farmboss cold and got that going. What's up with that.
I weighted some saws I had around for comparison
PS 5100 18" .325 1/2 full 15 1/2 lbs.
PS 510 " " empty 15 1/4 lbs.
PS 540 18" 3/8 empty 14 1/4 lbs.
PS 6400 20" 3/8 almost empty 18 1/2 lbs.
Poulan Pro 335 18" .325 1/2 full 15 3/4 lbs.
Husky 372XP 20" 1/2 full almost 19 1/2
041 Farmboss 20" 1/4 full 18 3/4
PS 401 Dolmar 16" empty 11 3/4
xl12 16" HN almost full 17 1/4
Poulan Pro 505 24" 1/4 tank 21 1/4
To me it seems ideal for hardwood up to what it's 18" bar can handle for a one saw arsenal. You can limb and block effectively. I wouldn't go to a longer bar myself,taller folks may like a longer bar for knocking off limbs when a tree is down. Why it has to weigh more than the PS 540 I don't know. Get the convenience features of the 5100 on the 540 without gaining weight and then you would really have something.