Among other things, they were selling the popular Knock Out roses (hardy only to -17ºC, 0ºF) and blackberry canes (usually hardy to zone 4 or 5). They were also selling a variety of bulbs and roots, some of which were hardy and others not, with no clear indication of what would survive in our area. Although the store advertised a one-year guarantee on all trees and shrubs, they probably count on most people losing their receipts before they notice that none of their new roses made it through the winter.
They were also selling tomato plants, although it's definitely to early to put them out, as evidenced by today's snowfall. Although it's a national chain, they need to understand that their garden centres can't carry the same stock at the same time, across the country. And while it's fine to sell plants that aren't rated for your zone, there should at least be some indication of that fact on a label.
So while you may find good bargains at hardware store garden centres, you should know exactly what you're buying before you purchase, and save your trust for a reputable garden centre.