It's good for priests to be familiar with both of their healing specs. You will probably get relief from the mana issue if you give discipline a try, and work on getting Archangel into your healing rotation. At level 40, I'd do something
like this, with glyphs Penance, Divine Accuracy, and Levitate. Check out the
Smite is Awesome thread here on the priest forum. I've been loving my smite spec. Although I am dual spec holy, I'd rather smite heal (when you smite and have Atonement, you automatically heal the lowest nearby target for the same amount).
I find using Power Auras to tell me my stack count on Evangelism (stack 5 before Archangel if possible), and when ArchAngel is off cooldown helps. Personally I have it show Holy Fire cooldown also, which is useful if later on you decide to use the smite glyph.
You want to be able to smite the tank's target and your own easily. I show the tank's and my target and use Vuhdo to bind my hostile spells to my mouse. You could also use Clique or another healing addon that lets you bind to hostile targets. Focus is also good for setting the boss in a frame you can click on anytime. Another option would be to show targets and keybind smite and archangel.
I'd also macro inner focus and PoH together to conserve mana (one free PoH ready every 45 sec), and increase crit chance for procing divine aegis bubbles (when you are higher level) on multiple targets.
If you decide to give it a go, spend a little quality time with the training dummy to get comfortable with your rotation and elements of your ui.
Edited, Oct 24th 2010 7:39am by dadanox