I just finished the game, 24 hours needed (due to a hard crash I have yet to see just how much I'm at, but considering I've done pretty much everything but the collectibles and a few leftover clusters it should be in the close to 100%.
I loved the story, the side quests were...repetitive at best, I decided to just skip it and do all the activities ahead of 'm to save myself some time, super homie missions were cool though.
Once you map out the keys for the superpowers it's quite easy to switch around with 'm on the fly (having more than 3 buttons on your mouse makes this a lot easier).
Some of the Mayhem missions were.... frustrating.
Many laughs were had, and like some reviews said I too felt sad when it ended, not because it was a sad ending or anything, but because you know that you've hit the end-game, and that somehow tends to be less entertaining than the journey towards it.
I do hope that the toolkits prove to be as powerful to SRIV as TES5Edit is to Skyrim (which is quite a moddable game). This game has such great modding potential because it has so many systems you can work with inside it. Truthfully, I believe this has much more modding potential than Skyrim.
*Potentially Spoilerish*
I do wonder though...is there really going to be a fifth iteration of this series?
I ask this based on certain events having me question just...where... it should be taking place then and how such a...place...would really work out compared to where it used to be.