I watched the Fourth Doctor Story: "Destiny of the Daleks."
It was my introduction to Romana (unless you count the briefest of scenes from 'The Five Doctors). It was also my first non-McCoy serial in quite some time. Now I have seen some of the Fourth Doctor before, but this was a welcome return. After spending so much time with McCoy, it's nice to watch the show when it actually getting a decent sized budget from the BBC. This story really blows away most of what they did with the Seventh Doctor.
As a Dalek story I found it really fun, and intriguing. The liesuresly pace threw me off at first, but by the time the Daleks showed up and captured Romana I was hooked. I was really pulled in by the story, and I loved seeing Davros again, I never get tired of seeing him.
I still intend to finish off McCoy's run, so I may watch 'Ghost Light' next, but part of me wants to explore some more of the early serials. I still haven't really watched anything from the Second or Third Doctors (again, outside of 'The Five Doctors).