Howdy.  New to the forum, great source of info.  I'm still trying to decide between an Aimpoint and an EOTech.  I heard someone mention a 'Rev E' EOTech.  I can't find any mention of this on their website.  What does Rev E mean, and how is it different from the 552?

The various revisions of the EOTech sights are just changes made to the same model.

Rev E is the newest officially available revision of the models 551 and 552, featuring raised rubber buttons and better water/shockproofing.

Does that also include the new extended battery life?  I read on an older post that someone said he upgraded to a 551 Rev E for the longer battery life, but the EO Tech website shows the 551 having a life of 100 hours, not 500 like the 552, so that doesn't make sense.  And it doesn't say which models are Rev E.  

There is no more Rev codes with EOTech, throw that out of the door.  EOTech no longer will release the rev code of the model they build.  What ever you get new on the market will be the new version.  

go here and read the review, you will gain a better understanding of the sight.  if you have any further questions afterwards, i will be happy to answer them for you.

[url]http://groups.msn.com/TheMarylandAR15ShootersSite/eotech1.msnw[/url]

The EOTech models that you are referring to, the 551 & 552 are the military models with the night vision settings.  The 551 uses  "coin type" batteries and the 552 uses conventional AA batteries for the longer life (which also makes the length of the optic a bit longer.  If you don't need the night vision gear settings they have tactical models 511(coin type batteries) & 512(AA batteries) availlable somewhat less in price. If you purchase current production optics they will be Revision E (which I believe gives longer battery life even in the models with the coin type batteries).

511 or the 552 uses N batteries, it is not a coin battery.  The N cell battery will give approximately 150 hours of life, and the 552/512 the AA version will give about 500-800 hours of battery life.

I stand corrected on the N batteries, I appologise as I had not seen that type, only those w/ the AA batteries.  As far as the different models go, reading from EOTech's brochure: models 511.A65/1 & 551.A65/1 use the N batteries and are 4" long, models 512.A65/1 & 552.A65/1 use AA batteries and are 5" long.
The current models will run continuous on nominal setting 12 for 100 hours w/ the N batteries and 500 hours w/ the AA batteries.