I already have 7As (which I use on the kit) and 5Bs which are used mainly on a practice pad but after injuring my wrist a month or so ago, I thought that a heavier stick (for use on the pad) would help me to rehabilitate and allow me to build more strength. So far, things are going very well - I have large hands in any case so holding the larger diameter stick is not a problem and my wrist is already feeling more stable after 10 days of work.
There is no temptation to use them on the kit, but I believe that anything which makes practice more interesting and fun has to be a good idea. I grabbed a quick snap of the new sticks alongside a pair of 7A for those of you who may not have seen them in person.