I understand that some people prefer healing with targeting the player rather than mouseover, but I actually found mouseover helped my healing much more, especially the faster heals were getting cast; since I lost time in the targeting of the player, then pressing the button to cast the spell. I find that most of the time, I don't have the opportunity to map out heals 3 heals in advanced, especially with cast times on all of them. Either by the time I get to person 3, they're dead, or have already been healed. (That is generally, there are times when I get to person 4 on the mentally tallied list with success also)

Anyways, I noticed the mouseover macros presented at least in this page, are of the mouseover only variety. The link to matticus shows another variety, which allows you to heal on mouseover, as well as by targeting, so you have the flexibility to do either or in the same button press. (example)

#showtooltip Cure Disease
/cast [target=mouseover, exists] Cure Disease; Cure Disease;

In addition, I have made my own modification to the basic mouseover/targeting heal macro, which allows you to double it up with an offensive spell. I particularly find this useful, as I have a limited number of keys which are within easy reach of my fingers and this increases the spells I can cast easily by nearly double. This could be useful for people who like mousovers in general, and are looking for ways to save keybinding space: (example)

#showtooltip
/cast [@mouseover,noharm,exists] Heal;[@mouseover,harm,exists] Smite;[noharm]Heal;[harm]Smite;

The macro above also works if you target as well, and is what the second repetitions of the spells at the end are for enabling. What I usually find myself doing is mousing over someone to initiate a heal cast (with boss targeted, so I can watch for any abilities/casts he does), and moving my mouse away from the grid layout to cast a quick smite on the boss, allowing me to trigger archangel for mana gains, before going back to healing.

Mainly offering these up as examples for people interested in mouseover-type macros, since you did suggest posting advice for it if we had any. Hope it helps anyone interested!

(Also, these macros I haven't had to update in a while, so there may be new changes which would allow for some shortening of the script. However, they all currently work fine, so I don't change them. And as with most macros like this, just replace the example spell names with the spells you would like. :3)