I love OOOs. The story is kinda loose so far, but when I think about it, most Heisei series were like that till around... well, now. (30 some episodes in)
The cast is one of my favorites. Kougami, Date and Dr. Maki are god tier, Ankh and Eiji are awesome, and Hina is actually pretty nice for a supporting female in a Rider series.
I love the medal exchanging gimmick, watching each side gain and lose medals, and Eiji making do with what he has. I'm not too happy that solid combos are just the best, and Eiji rarely uses the abilities of mix-matched medals in unison, but I find the solid combos to be more aesthetically pleasing, so this doesn't really bother me in the end.
I gotta say though, while the Greed are pretty awesome, a lot of the Yummies are some of the weaker monster designs, overall. There's a few good ones, like those two beetle monsters, and the panda/orca Yummy had some charm, but most of them are completely uninspired.
But the 999th/1000th episodes really blew me away, that's for sure.