We had somewhat similar experience at our REI.
The most local LBS isn't a lot better. I bought my used Trek Remedy 5 from them - nice bike, but the prep & support was kinda "meh". When I told hime the back brake felt weak, he showed me he could lock up the wheel... on the tile floor. I pointed out that tiles are slick, so he lifted the back wheel & showed me he couldn't rotate the wheel with the brake lever pulled. I said I probably could... so he pulled the lever, and I rotated the back wheel (I'm stronger than I look). I really liked the bike a lot, otherwise I'd have walked. But he only did a very basic suspension setup - put the air pressures somewhere in the mfrs range (didn't ask my weight or riding style). I do get warranty & tune-ups for 60 days, which is better than private party sale. But it won't be the first place I go when I shop for a new bike.
We found a LBS in a nearby town that the owner seems really great.
We actually ran into the owner while flying kites on the beach. He wasn't pushy at all - quite the opposite. We went in... and we'll probably be buying my wife a bike from him on Saturday. He doesn't have much inventory, unfortunately - and only sells a few brands, I think... but I liked him enough that I'll shop there when I'm ready to buy a new bike (though I usually buy used because of budget).
I wish more dealers sold used bikes. Some of them take them in as trades, but either donate to worthy charity organizations, or bulk sell them to others who resell them.
It's an under served market, IMNSHO.
CraigsList, Offerup & Pinkbike are good sources, but it eats up a lot of time having to drive to people's areas to see used bikes instead of being able to see a selection of used bikes in one location.
I guess stores like Play It Again sports might be a source.
But now I'm rambling.