I read up on this a month or so ago, so a bit fuzzy... but I remember thinking that it was VERY limited in the number of "lessons" on it. Seems like a great idea, but I'll be waiting for a more comprehensive set... or perhaps there will be plugins/expansions.
As far as learning to sightread: I know it's hard, and many of my students complain about it, but DO IT. You will be so amazed at what you can accomplish so much faster as a reader. For example, do you guys read Modern Drummer? If you can at least hack through the lessons in there every month on your ZD, you will be SMOKIN' in no time- esp. Jazz Drummer's Workshop stuff, and the transcribed drum solos.
You'll also get the benefit of "seeing" rhythms in your head as you're listening to music... instead of trying to memorize everything by ear, you'll have another frame of reference. And 3x5 notecards with a quick arrangement and 1-measure sample rhythms written for different sections can be a LIFESAVER. I did a recording session once... I had 2 days to prepare 20+ songs. I listened to them ONCE while scrawling some notes, got to the rehearsal, and I knew the songs better than some of the guys who were IN the band. Invaluable time spent there!
Another hidden benefit to being a reader is being able to communicate with the rhythmic language. You'll be in a rehearsal and someone will say "how does that rhythm go again?" and the readers in the room will have the tools to communicate this accurately and quickly, without having to take the time to play it 700 times until everyone just "feels" it.
Get ahold of a simple book/CD package and get to it! It will be worth it, guaranteed.