Actually had a pretty good experience a few months ago as well. Was helping a family member buy a prebuilt, and I figured we'd go by Best Buy, but didn't really expect to find anything. Anyway they had a cheap Compaq system for $280 (cheapest Walmart system I think was $300, the the one at Best Buy was slightly better). But here's the kicker, they had a combo deal where you could add an 18.5" LCD monitor for a total of only $292. The monitor's a real cheapie, but for $12, why not? Turns out it was a pricing mistake, and we didn't even make a fuss about it, but the sales rep insisted they would honor it. Was kind of surprising to me, because I'm used to buying online, and if there's a pricing mistake they usually just cancel the order. I certainly didn't expect them to honor the $292 price, but it was nice that they did. Maybe the laws for B&M stores are different and they're required to honor sticker prices.
Also they didn't try to force any protection plans or other BS on us, which was nice. I figured they would really try to push stuff like that during checkout.
tl;dr: Went to Best Buy, got a pretty good deal on a computer and monitor, was a surprisingly hassle-free experience. But YMMV, I've heard my share of horror stories as well.