I used them a few times many years ago when I had a cheap offset smoker, thinking I'd save money on smoke wood. I don't recall them imparting the same flavor as wood chunks, but I found that they seemed to burn faster. Combined with the slightly higher cost, I'm sure I lost money on the deal.
Nowadays, I wouldn't use them for smoking/barbecuing, but they'd probably be good for hot/fast grilling when you want a bit of smoke flavor.