I went on Abu's website too a couple days ago, I couldn't find them either.
Yes the Revo S is awesome!
You can get them on *** however, no they are not discontinued.
Gen 3 is the latest, and in my opinion magnetic breaking system is better for beginners then again I like centrifical breaking system.
After awhile i started to like them both breaking systems, some reels have them together in one reel.
And how to set a Baitcaster's breaking system: http://www.bassresource.com/bass-fishing-videos/adjust-baitcasting-baitcaster.html
When casting a Baitcaster: http://www.bassresource.com/bass-fishing-videos/how-to-cast-baitcast.html
If you fish heavy cover slop, mats, grass, weeds, etc. You'd want it thicker near the reel seat, line weight is what pound test a line can "properly" handle. I sometimes go over the limit, haha. Lure weight is what the rod can cast with "ease" I go over this sometimes too. Power means means the action of the rod or the how easy it can handle cover/fish/lures.
I started with Abu Garcia caught my PB with them, when I just started using Baitcasters.
Hoped I helped!