I don't mind the new theme. It's not quite as 'sing-a-long' as the previous one but it's still got a lot of energy to it. I did like how Jin and J are now integrated into the opening sequence in a way that Sentai has never done properly before. The new ending dance wasn't as good though. It doesn't fit the music as well as the original one, and while I appreciate that they're putting much more into the dance moves, it was a bit much for me. Again, good to see Jin and J brought into it properly though.
As for the episode, well yeah for the most part it was mostly a fun filler episode. Decent enough story to keep you interested, and right at the end a bit of setup for what will hopefully be a proper 'plot' episode next week. I did think Enter kind of jumped to conclusions though with his assumption that Messiah was evolving (how did he know it hadn't just put an error in his code and crashed his master?).
EDIT: THAT theme tune. Total earworm. It's been going around in my head constantly since I watched the episode and I've ended up playing it over and over for the last four hours. It helps that I like dance music, and I'm sure if you don't it's not a good theme, but it's grown on me amazingly quickly. Though they should have taken the robot voice saying "Busters ready go" from the full version and put it in the OP too!