I liked the series a lot from the beginning. I was a big fan of his more unusual design, the space theme and the over the top sillyness is a bit different for Kamen Rider (at least the past few seasons). I wasn't sure how I'd react to the school setting at first, I imagined it was going to be pretty generic Japanese anime stuff, but I'm glad they really went in a different direction with that.
But as others have said, the second half of the series seemed to fall apart. Meteor's plot dragged out far too long and then when they finally ended that arc, he basically stopped being relevant. His rivalry with Leo could have been great, if it didn't materialize from no where in the last two episodes. I really liked his design as well, until they completely ruined it with his Storm upgrade, which I think was used in every single fight scene from then on. He quickly went from being one of my favourite riders, to someone I didn't care about at all.
I also have to criticize them for using the same plot with the partner/friend character for the third time running and for the fact they just randomly bring him back at the end. I don't mind if they want to include a little melodrama, but what's the point of the big teary farewell, only to have it be a complete fake out? I didn't fall for it for a single second this time and that really hurt the tone of the final episode for me.
Bottom line.. I think there was a lot to like about this series, but the plot felt very rushed and poorly thought out towards the end. If they took advantage of what they had, it could have been a great series. Instead, I'd rate it as merely okay. I don't think it ever became unwatchable, it just could have been so much better with a bit more planning.