The craze to have this ''stack'' or ''stack clap'' or ''slap stack'' or ''slap clap'' .. - the names are countless.. - finally got to me, as I purchased the damn thing. I must say it's a great addition to a drummer's ''repertoire'', as there are countless uses, despite it's just a ''clap''. I use it instead of snare - alone or in combination with rim-click - unison or as a flam, or even in some ''drunk'' groove (if you're a drummer, you'll get it)...
Then I have to talk about the addition to the fills! Man oh man - you can really go crazy with the countless combinations to include this thing - speaking of more ''chopsy'' fills... As I got really into stuff from for example Jost Nickel and JP Bouvet, this ''toy'' as I see the SlapStack really makes me happy when I play. And I shouldn't forget to mention this: every time I brought the thing to a gig, fellow musicians just LOVED it!
If you're not a ''brand snob'' just buy the thing, or else choose a product from other well-known brands, but I tell you - those (despite way higher price) are the same...
Hope it helps :)