"HOVERING AND TRAILING" as one poster put it. That drives me nuts whether it's a clerk in a store OR a waitress hoovering over us at a meal. I have been known to politely say to a pesty server "Thanks.. I'll flag you down if we need anything else".
To the overly helpful LQS owner I'd politely say "Thank you, but I do MUCH better if left to browse on my own. I'll let you know if I need help".
At least these helpful folks are erring on the "positive side"...and not being overtly rude. NOW.. if your polite comment triggers a negative response...then.. I'd for SURE spend my money elsewhere.