This is exactly what I was looking for.  In this review, I will offer you a full product review, as well as some tips on how to actually get this thing on.  I am a size 18 (big) dress shirt (according to JC Penney size chart), I wear a an XL - XXL t shirt.  Honestly, an XL fits me, but my man boobs make me feel uncomfortable in just an XL...so I usually go with the 'bed sheet' size.  I have been wearing Under Armor, and similar products for 9 years to try and keep my jiggle from jiggling, and my man boobs from making me over-self-conscious.  I am 5'10 and 275 lbs (as a reference point), and I am built pretty proportionally with a 53" chest (using a measuring tape) -- man boobies and all.

This is the only product that literally reduces my shirt size by 1 on the t shirts, and 1.5 on the dress shirts.  My body still looks large, but naturally toned and not jiggly.  It is ultra comfortable (i.e. zipper does not dig into my skin, the interior 'latches' do not poke me funny, and the quality of the material is very high.  This will be infinitely more durable than Under Armor is.  Under Armor is too thin, and stretches out over time.  This is (seemingly) made of a much denser, and thicker material.  It is not scratchy, or uncomfortable at all though.  That I am shocked with.  I look great in this...even though right now I don't REALLY look great.  This will at least help me feel decent about my body while I lose weight.

As for the sizing issue many people have been talking about.  You have to know how to put this on, or you will think it is WAY too small.  When I first tried it on, I unzipped it, unclasped it, and put it on.  I then tried to re-clasp it (which was disappointingly hard), and then tried zipping it...which was literally impossible.  I tried laying on the bed, jumping up and down, sucking in my fat, stuffing my fat in the side, etc.  Tried everything...and it didn't work.  I was beginning to think that every review was right about the sizing being ridiculously wrong.  Then I thought outside the box...

I tried clasping it, zipping it, and then pulling it over my head.  It was extremely difficult to do at first, but the more I have done it, the easier it has gotten and there is a method to it.  If you roll up the body portion all the way to the neck line, slip it over your head, pop in your arms, and then unroll it down your body, it works infinitely better.  It is still a very (very) snug fit, but it is not uncomfortable.  It does not restrict my breathing or my movement in anyway.  It is very tight...skin tight....but that is exactly how it is supposed to be folks!  I can't really offer any more praise for this product, or any additional help.  I have laid it out pretty simple.  If you are looking to make yourself look MUCH thinner, much more toned, and feel much better about yourself while you work off the extra weight.  This is (without a doubt) the best thing money can buy.  It is awesome.  Please ask any questions you want, and I will try to answer them to the best of my ability.

**NEXT DAY UPDATE**

So, I wore this for a full day, and I have some further information regarding the product.  I am definitely not reducing it from 5 stars because it is fantastic, though there are some things I wanted all of you to be aware of.  First, after an entire day of use, there were some noticeable imprints on my skin from the zipper, and some discomfort on my skin.  So, I decided to go ahead and use a bunch of my old and stretched out under armors underneath the vest.  So far, it is one million times better.  Much, much more comfortable...and less uncomfortable marks.  Another thing, if you wear t shirts with it, there is a slight protrusion in your chest where the zipper is.  It is the biggest disappointment of the vest, but it is not deal breaker for me.  I have found that any t shirts with lettering or a design....or thicker t shirts do not show the protrusion that badly.  Anything that is really clingy or really thin tend to show it a little more.  So, this is certainly not as amazing as I once had thought; but the results are still the same and they are still very impressive.  I was able to fit into one of my favorite dress shirts again, and my man boobs and rolls were not as embarrassing.

** UPDATE 8/13/13  **

So I have had this for 3.5 months now, and I am still incredibly pleased with it.  Yes, it has stretched-out a little over time, but, I have also lost 25 lbs since I first started wearing it...so it might not be getting stretched-out as much as I am thinking.  Regardless, it still keeps all the 'jiggle' firm, and I am still fitting in shirts a size smaller than I am.  Without this, I can wear 18.0 dress shirts (Van Heusen) rather uncomfortably, but they fit.  With it on, I can wear 17.5 - 17 rather comfortably.  The biggest issue I have with it, is the portion of it that goes over the shoulders has stretched out a little (it is like Underarmor material), and so I typically have to pull the whole vest down a little further for the shoulder straps to work properly.  I have thought of cutting them and sewing them, but am afraid about the ruining the fabric and being unable to sew it back up adequately.