You can combine 3 inspirations of a single kind into a single inspiration of any other kind. -- Live
You can save your costumes out as files and reload them. Same with power customizations. -- Live, I think
Oh, yeah, you can customize your powers now. -- Live
You can invite your own alts to your supergroup with /altinvite -- Dont know
If you have a mission you've outleveled in your mission log, try abandoning it and retaking it. Often the new version will be re-scaled to your current level (I think up to some max per contact). -- Live
The little chat balloon in your chat window is a popup menu, chock full of a bunch of fun emotes and stuff. You can also use it to change your difficulty setting and effective team size. -- HC, I think
Oh, yeah, you can change your difficulty and effective team size now. -- Live, via Hero Corp Analyst
You can use the auction house from just about anywhere with /ah -- Live with the requisite Vet badge, 84 months
You can change a bunch of settings, including your alignment, by talking to Null the Gull in Pocket D. -- No idea