Healbots functions. I have here chosen the easy way and quoted from wowinterface
(WoWInterface Downloads : Action Bar Mods : HealBot continued)
Evaluation
Ever since I started healing in the autumn 2007 I have used healbot because it has all the options I need to heal effectively. As a person who's not very good at using addons, all the options in healbot where pretty overwhelming in the beginning for me, but compared to other addons it is user friendly. But without having healbot configured properly it can hamper your healing effectiveness. I will evaluate each tab in healbot individually to make it easier to get an overview. All in all I think it is avery good addon but with a few major flaws. Healbot has been rumored for taking up allot of memory but it only takes up 920 KB for me both out and in raid.

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General: The options works fine. I just want to warn against fluid bars. My guess is it is there to make it easier to see who is losing health, but it delays your calculations about how much a person needs to be healed. Having the function on to show who has agro can be use full.

Healing: Gives option in who in the raid to show and who are to be organized together as a group. This can be group, class, tanks and pets. There is an error on healbot which sometimes makes tanks healthbar disappear in the middle of combat and you cannot make it reappear while in combat. This is very annoying and potentially wipe threatening.

Spells: enables you to heal by taking your mouse over your targets healthbar and click to heal/decurse/buff the person also called mouseover healing. I have a G9 mouse so healbot does not allow me full use of my mouse, but not all buttons are in good position for a quick reaction. So it does not mean to so much and I have a special setup with my mouse itself when I play wow giving me close to full use of my mouse. My main healing spells are just a simple click away. rank 7 and 12 healing wave. Chainheal rank 5. Lesser healing wave. I depoison, remove disease and other ranks of healing spells by using shift, ctrl and alt then clicking with the mouse. I move my character both by keyboard and by mouse. I cast my totems by mouse clicking on my totem addon. This is all in all working quite well for me. It it also possible to put macros in mouse clicking but I have not tested this myself.

Skins: I can configure the healthbars in the size and colours I want. It has several options for the graphic on healthbars and headers. I find headers use full, it shows group number, tanks, class depending how you setup the groups under Healing. I really like the bar opacity options. You chose how much a healthbar is faded out depending on full health, incoming heals and disabled.

Debuff: It can show who is cursed, poisoned, affected by magic and diseased in the colour of your choosing, but it can only show one of the debuffs at the same time.

Monitor missing debuff: Because I am a shaman i have never tested the buffing options.

Tips: With tool tips information on there is to much information to read with a small text size , to react quickly during raid, so I have it turned off.
Bar information works fine, but if you try to have to much information on the bar you cannot read everything. A players missing health overrides the name, which I do not find a problem. I always have class name turned of bar, because I know which classes my guild members are and because class can be shown by the colour the characters name is written in.
HoT icons is for your own heals, but it does not display gift of the Narruu.

Incoming heals is shown with other healbot users, but HoTs are not shown. There are a few others in my guild using healbot which it exchanges incoming heals with, but it does not exchange information with grid, so the amount of incoming heal shown is very limited for me.

Your startup memory doesn't mean squat, it's the increasing rate of memory growth that you want to be concerned about, and the cpu usage it consumes.

Me personally, I hate these type of addons, it's just clique, grid, ctra, decursive and some macros all combined to make 1 addon, you might aswell just zip those mods up and you have the same deal.

I checked what the memory is in raid and it does not increase at all ro very much. The reason why I say the memory usage in and outside raid is 920kb

I've found HealBot to be invaluable to helping out healers who are new to raiding, and may not have used click-casting healing addons before. As mentioned above, you can get better functionality by installing a slew of addons, and configuring them to fit just right to your class/healing style; the benefit of HealBot is that it puts all that together for you. Once a healer becomes more accustomed to operating in that manner, if they want more customization, the other addons are more useful; HealBot can't be configured very much from it's base structure. But overall HealBot is quite handy, and functional for standard raid healing.

One thing I'm finding fantastically annoying, is the facility in healbot to show lifebloom - if it can show it, it certainly takes some meddling. It's not worth spending any of my 'loose' GCDs tossing lifeblooms into the raid, when a priest playing whack-a-lesser-heal will overwrite it before it's bloomed.

Get them to install grid and click2cast, and set up some indicators for other class's HoTs - I've been in enough wipes because classes with straight-up heals can't leave a bloomed target alone that they've run OOM.