Actually on the topic of UI related issues:
I know a lot of people, enable/disable certain mods while raiding. I highly suggest
http://www.wowinterface.com/downloads/in...mpere.html
Its an incredibly small (50k) addon that mirrors the button on the log-in screen, in game. It allows you to enable and disable mods on the fly without the need to log out, wasting more time than necessary.
http://www.wowinterface.com/downloads/in...rlock.html
I know a lot of people miss classtimers (idk if it has been updated at this point or not). This mod works just fine. It has a slew of options over and above simple spell timers (incl cooldown timers, etc) but uses roughly the same amount of memory. I switched over to this after seeing just how fucked classtimer was on the ptr and I dont see myself going back any time soon. It was originally designed for warlocks, so there are a lot of additional modules that other classes will probably want to disable but overall I have really come to love this mod.
If you have the patience,
http://www.wowinterface.com/downloads/in...assic.html is another great alternative. It can be set up to monitor and provide visual cues for cooldowns, spelltimers, procs, trinkets, etc etc etc.
Finally, some of us with less than stellar computers will notice that some unit frame addons are disgusting memory pigs that will destroy fps. I suggest
http://www.wowinterface.com/downloads/info9994-oUF.html with
http://www.wowinterface.com/downloads/in...ivaya.html. These unit frame addons use incredibly tiny amounts of memory. The general drawback to most oUF layouts is that the only way to modify them is through editing lua. oUF_Nivaya is one of the only oUF layouts that offers in game customization. Due to its basic nature, it isnt for everyone. However, if you need a unit frame mod that wont bog you down during raids you should give it a try.
(I know Im rehashing a lot of shit from the UI thread, but if these will assist some people, it cant hurt)