I have used Stansted a few times recently including Christmas landing back around 2200 and I have to say a massive improvement. The longest I waited at immigration was about 10 minutes. That really isn't bad considering it's size and the amount of inbound Ryanair's at this time.
Also similarly the outbound experience at security has improved. I walked straight up last time, totally unexpected. It seems there are two entry points for security... The main one that everyone heads for and there's another entry next to the fast track, to the far right of the main entry point. Much quicker in my opinion.
Now they just need a revamp of the check in area. All those white washed walls that were put up with the terminal redevelopment look shabby and temporary.