I bought the Aerocool 500W from newegg.com because it got great reviews and Tomshardware.com did a build with one...but supposedly its on Tier 4 of "the list", and people are whining about it.  
 
What's the deal?  Should I send this back before I build?

Don't Always believe the "Tier List".
Especially unless they list a very specific models.
 
AeroCool has a wide range of Power Supplies.
Some are quite cheap, others are not.
 
The "ZeroDBA" line is a good PSU.
You might quibble about where it belongs on the tier list, but this is not a "Tier 4" model.
 
If you note, NewEgg lists other AeroCool models with more "Watts" but for a lower price.  These are lower quality AeroCool Models.  There are even other models that are prices even lower and yet again lower on the scale.
 

I see you excerpted this from your previous post about your new system.  I had already responded there but since this is about the specific item I addressed, I will repeat part of my response here for the benefit of those who pick up only this thread.
 
Your AeroCool PSU may be fine for a mid-level system.  However it has no PFC - power factor correction, does not have the power for SLI or Crossfire on better GFX cards, and only mediocre efficiency - meaning you might use about 10% more power over the life of the unit - which can more than offset the lower price.  Also note that it only has 4 SATA connectors.  A couple of optical and hard drives will max it out - but it might be enought for you.  The Corsair 520HX also has 4 SATA connectors while the 620HX has eight.  
 
The PSU was reviewed by JohnnyGuru.com - a very reputable site.  Here is the review and their summary.  
 
http://www.jonnyguru.com/review_details.php?id=16  
 
SUMMARY:  
 
The Aerocool Zero dba 500W is a nice little power supply for a single PCI-e or lower end SLI or Crossfire machine (like dual 7600's or dual X1300/X1600 cards. The fan is quiet and the controller knob works well, and if this is for a computer with a big window that shows off the insides of your PC, then the super shiny chrome finish and black sleeved white cables will look fantastic.  
 
Good...  
 
Looks totally rad, dude!  
Stable voltages  
Modular  
Fan controller keeps fan from spinning while PC is idle  
135MM fan is quieter than typically used 120MM fans  
Fan only connectors  
 
Bad...  
 
Simply not enough power or PCI-e connectors for high end SLI or Crossfire  
 
Mediocre...  
 
No PFC  
Mediocre efficiency  
Cables are very stiff

Thanks guys this helps.
 
The cables are kind of stiff by the way.  Maybe i'll order some new stuff while i use this power supply and if I like the new stuff I'll switch it out.