Character rating sites such as Be Imba and WoW Heroes provide a benchmark for your character, or any character you desire. You tell it who to look at, and it will give you a rating of how good that character's gear is. Does this have any value besides bragging about the size of your score? Well, sure, but they are not equal.
For the more casual player, these sites will give you information that can help you improve your character. So let's see what kind of information shows up.
This is the screen showing Be Imba's analysis of Myze's tanking gear. As you can see, it is in "Top Shape." All the items are level 70, There are no inappropriate gems or enchants. I'm even just ever so slighty uncrittable, showing I've made the most of the rest of my gear. In a typical Karazhan run I have about 20K health and 35K armor, just below the armor cap. So I would say I'm doing pretty well for myself, and Be Imba seems to agree. It places my gear upgrades as coming out of SSC and TK, and my performance level to be that of a Druid who's seen about half of Hyjal and Black Temple. The one thing that bothers me about this is that it suspects that my talent build is suited for PvP best (though I have no Nature's Grasp or Swiftshifting or other related talents) and then grinding second (if that were my goal, I'd definitely have Savage Fury instead of Shredding Attacks.) No, I am 100% Raid PvE and thus I think there is something amiss with this algorithm. This could cause someone to change a perfectly good build in favor of a subpar one. But this is a minor quibble. A more major one is the wait times incurred when processing the reports. This site takes forever. But it's pretty accruate.
This is WoW Heroes report. The interface is cleaner, there seems to be more information out in the open, and it's much more colorful overall. Of course, most of it is information you'll get from the Armory. You can see a rather cryptic gear score at the top which is shown the be a composite of gear + enchants. It also seems to think I'm not BT material. Folks, I've been in Black Temple, I'm more than capable of keeping up with the rest of the guys. This is misleading, and if a guild leader tries to use this as an excuse to exclude you from a run, go find a new guild.
The "value" for each item is merely the iLvl, I don't see what that has to do with the quality of the item. There are certainly higher ilvl items than Band of the Swift Paw, but none are better for tanking. I also don't appreciate the fact that my enchantment choices are "subpar" though "upgrading" them would result in crittability and ultimately serve as a liability. However, the fact that it does try to point the user in a better direction by suggesting enchants is welcome, even if it's wrong in my (admittedly corner) case.
The usefulness of these tools is limited, but it does help keep a guild leader abreast of members that are lagging behind in gear. For example, I've looked over the scores of my guild in both utilities, and my healers are most consistently at the bottom of the list. I will likely offer guildance on gearing to them, but I don't believe in forcing my members to use outside resources, so I will have to live with how they gear. Fortunately, they all seem to care about their performance, and have already spotted their own room for improvement. So I will wait.
All in all, these tools provide a quick summary of a characters projected effectiveness. Be Imba is more accurate than WoW Heroes, which is easier to read and much faster to generate a report. In either case, take the information given with a little grain of salt. Use your own judgement and tools more specific to the job. I recommend Rawr for feral Druids, though I cannot vouch for the accuracy of the other modules. Try it.