Yep, got a pair and wouldn't be without them. Very useful and fill an important gap when grilling. When grilling, you can heap the coals on one side or the other and do some indirect grilling (lower temp's for example, like veggies maybe) and that works, kinda sorta. I like to use the baskets you mention, one to each side when I'm using the rotiserrie with my kettle. With the chickie getting heat on both sides, well, it's an experience you've got to have to appreciate the kettle. That's just one quick example of their use.
Another item to keep in mind if you go with the baskets is the grill grate with the flip up ends, next to the lifting handles. With the baskets situated under the flip ups, you can easily add charcoal or lump without having to disturb the grilling process. For 15 bucks and change (depends on your local tax collector), a worthy investment.
~Dave