I enjoyed the match quite a bit. The storytelling worked out nicely with Cena still looking like the courageous, never say die good guy while Lesnar still looked like a beast. All in all, while the match was far more even, I got the notion that Lesnar still ultimately looked as though he came out ahead of Cena. He'd already thrown everything & the kitchen sink at Lesnar several times, namely numerous AA's and STF's in the center of the ring, while Lesnar had ultimately beaten Cena around the ring, hit some suplexes and had the Kimora locked on a few times, yet he hadn't hit Cena with the F5. Lesnar looked like he'd taken all of Cena's biggest guns and managed to survive while Cena still had the F5 to contend with. As a result, to me, while it was a more even contest, Lesnar still looked more dominant. Leaving Cena laying in the ring post match after hitting the F5 cemented the image.
As for Rollins interfering, I'd read something earlier in the day in which it was rumored that Lesnar had spent the day learning how to take Rollins' Curb Stomp, indicating that a cash in attempt could be coming. What surprised me is that Rollins interrupted the match itself, which I thought was a good use of the surprise factor of MITB. I mean, after all, cash in attempts have come usually post match when both competitors are "exhausted" and "hurt." I agree with F.A.T. in that the story seemed that Lesnar might have seemed like the one most vulnerable. Cena had really started rallying against Lesnar in the last 5 or 6 minutes of the match, he'd had him in the STF for a while and had just landed his 4th Attitude Adjustment of the night. There are also any number of directions WWE could go with it: Rollins could've been encouraged by The Authority to hit the ring and take his opportunity if it looked like Cena was genuinely close to winning. They could go with the notion of Rollins "going into business" for himself and taking it upon himself to seize the moment. They could try saying that there was an agreement between The Authority & Lesnar that Rollins would make his presence known if it even remotely looked like Lesnar was in trouble because The Authority don't want Cena as champion. In the process, Rollins could've decided to, again, go into business for himself by double crossing Lesnar and attempting to cash in, etc.
At first, I was a little put off that Ambrose wasn't the one that kept Rollins from succeeding, but it makes sense from a logical perspective. As has been mentioned, Ambrose was taken out of the arena zip-tied by about half a dozen security personnel, it could even be stated by The Authority tonight that Ambrose was arrested or that he was being held by building security until the event was over and was under constant surveillance. As a result, Ambrose couldn't prevent Rollins' cash in attempt. I like the simple, realistic notion of a guy who's taken out of the building in restraints isn't able to get back in for the purpose of raising more hell. It doesn't make security look like a bunch of incompetent boobs, something most fans aren't willing to suspend disbelief for in the first place because it seems like lazy booking.