I like nameplates, but I greatly dislike Blizzard's styling for them. It's too bulky and blocks your view of things beyond them. I far prefer having transparency to my nameplate mods, and throughout TBC, I used Aloft to personalize them: unfortunately, Aloft is a very resource-heavy mod, and since it uses the DogTag lib, it had conflicts with Pitbull as well as Cowtip.
So, in WotLK, I set out to find a new nameplate mod. I have two recommendations.
Cael comes as-is: no setup options, though if you reaaally wanted to, you can personalize it by digging through the LUA. I don't recommend editing LUA, however, as you'll have to redo the edits every time you update the mod. Regardless, I like Cael's setup and defaults, and really didn't feel a need to edit it from how it came. It's a great simple nameplate mod for someone who wants to see the plates and not be overwhelmed by them. I used these for quite a while, and plan to keep it installed in case I need to revert back to them for any reason.
2) Tidy Plates + Threat Plates
It's much heavier than the caelNameplates, but it has customization options and a wonderful threat detection system that I have fallen in love with (and it's not as heavy as Aloft!). Based on low, nuetral, or high threat, you can alter settings for colors, scale (bigger vs smaller plates), and opacity. Now, I did have to tweak some of the settings because the default "low" threat value had an annoying bright green glow (which you can see in the screenshot below), and I wanted them smaller than the default, but it didn't take much digging to find and make changes to these settings. It also has different options for tanks, who would be more interested in seeing the ones they DON'T have good threat on, and it can switch each time you change your dualspec. I am currently using this mod.
Ignore the power auras going off around the screen :D Below, the large red bars are ones I have aggro on as a healer; the smaller green ones (I have since removed the green glow) are ones that aren't trying to kill me.