Based on what folks were saying and based on how much I like my 7900, I got impulsive and grabbed a 5100s very recently as well.
Maybe I was expecting too much, based on my 7900.
First impressions;
Certain fit and finish details not up to my expectations. I know it is silly of me, but I like my saws to be purty at least at first. I've enclosed a couple of pics of the plastic around the handle where the pieces don't meet. Bothers me to look at it. Other complaints include the finish of the air cover is not smooth and telegraphs all the webings, etc underneath. Not very purty to behold, and a letdown compared to the 7900. Decals on the flat below grip already cracked.
Power seems less than I expected, but that also should improve with time.
The rear handle somehow seems a bit hard and rectangular compared to all my other saws. Not really a problem, especially with gloves, but surprised me a little.
The saw revs up very nicely, but takes longer than my other saws to slow down to idle. Not sure if I can tune that out, but it drives me crazy to wait until the motor slows down enough to set the brake or move to the next cut. It's idling close to spec and has great acceleration, so i am not sure what I can do about it.
Once at revs, anti vibe is good. Chain adjuster seems to work well.
Bottom line for me so far is that I feel I got a bit impulsive and for now I questioning my choice. But I had to know for myself, and I still hope to resolve the issues. I know most folks love their 5100s, so maybe it's just me. Or maybe since the serial number is very recent Dolmar is rushing to keep up with demand a little? I really want to love this saw.