For those of you that like to DPS on your Death Knights, I just recently discovered a nice little add on that has helped a lot with my rotation, particularly on boss fights, and has had a pretty noticeable increase on my DPS. The add on is called CLC DK and is available on Curse.com and Wowinterface.
It functions very much like Shock and Awe, and addon that has been used by enhance shammies for quite a while. It basically suggests the spell to use next based on priority rankings right in front of you on your screen. It also provides a better graphical tracking of your runes and can help track various cooldowns including Pillar of Frost.
If you haven't used it, I'd urge you to give it a try. The only downsides is it seems focused particularly on single target, so it's not necessarily prompting you to hit pestilence to spread your diseases. I also haven't figured out a way to get it to incorporate Blood Tap or Empower Rune Weapon in its suggestions, but I'm thinking I might just be missing that at this point.