@cryptopie I have been using Keychain for a while, and I really love it.
I only leave my posting key in the extension, and when I need my active key I just paste it into Keychain. Then I remove it after I am finished!
I just bought steem today, powered up, and delegated and then removed my active key..... very nice! :)
I am waiting for the IOS mobile.......
I think the only downside would be if you stayed signed in ,and someone got access to your computer, but when you close your browser it logs you out.