JAMUS  I switched to WowMatrix about a month ago and so far it has worked better than the WowAceUpdater I was using before this. I guess the big test was when the 3.02 patch came out in prep of WotLK. It found almost all of my plugins and has been keeping them up to date, which was a BIG deal considering all of the plugins that broke with the patch!  
(Version 2.9.3)

TUNDRAKEN  Why does this program take up 100% of one CPU in a dual-core system? Far too excessive for a "light weight program".  
(Version 1.61)

DREMWKR  WowMatrix 1.61:

It allows one shot updating of all your WOW add-ons, making this a big timesaver. It simply works. It has a clean easy to use interface. And its free.

This is an essental for anyone running WoW add-ons, in fact it should come with/ or be built into WoW. It is so good, having it is a no brainer.

I run WowMatrix not only after every WoW update, but also before every WoW session. After having running WowMatrix a while, I discovered that some add-ons have continous and rapid update cycles, that I would have otherwise missed just running it for updates.  
(Version 1.61)

AHAWKES  I love it. This is the first add-on updater that has met my expectations. I have used several and i have many add-ons. I recommend launching it before each time you play.  
(Version 1.5)

PABLO2K  this is great. It actually works as opposed to MacAceUpdate which looks like it haven´t been updated in a while.

Just drag it to your WoW folder, run, select WoW folder and press update  
(Version 1.1)

E_COMMERCE  Whoa, this is a complete rip-off of MacAceUpdater:

http://code.google.com/p/macaceupdater/

It looks like they did clean up the interface some, but the fact remains that they stole an open source program, rebranded it with no credit, and aren't contributing any changes back to the original source code.  
(Version 1.1)

GONEFISHING  Surprisingly, it works well, though I was quite skeptical at first. It is, however, a big processor hog, even when idling in the background. Not that this is a big issue, since it only took a couple minutes to update all my mods (and it actually did).

Pretty good.  
(Version 1.1)