I'm not sure how Steam would be worse than piracy for someone on usage-capped broadband. It would be better than BitTorrent, at least. And I think Steam lists system requirements for everything in its inventory, so though the refund situation still sucks, it does address the "Is my PC up to scratch?" question somewhat.

With piracy you can download it somewhere else and use a memory stick.

PC system requirements are still notoriously inaccurate. There are too many variables and the wrong combination of CPU, GPU, motherboard, memory bus, OS or drivers can make or break performance of a game. Minimum (or recommended) spec doesn't always mean that playing will be enjoyable.

You can actually backup&restore local content on Steam, so you can do the "download elsewhere then copy to memory stick" thing as well.

I don't think I've ever seen a store that accepts refunds on software the moment you open the shrinkwrap, so I'm not really sure how Steam is that much different.

The comparison is to piracy, not to lousy retail stores.