I have had no problems at all with all my cascade canisters so far, I have two 1500s in my 120 and one more in my 55 oscar tank, they work fairly good, maintenace is simple and quick, the few times I have to prime them it's quick (only when I clean tubing), instalation was simple.
I still see factory media for those canister's at my lfs, but after a while of having canisters you'll know that is a lot cheaper and works better to buy bulk and cut to fit, and buy large packs of bio-media (seachem matrix is what I like) and fill as needed, so even if media was hard to find I wouldn't worry much about it.