I have a pair of 505 in the same size as the new pair I ordered on Amazon.  The previous pair was bought on sale at a local Fred Meyer.  They were durable and fit well.  They actually lasted over a year with frequent wearing and once per week washing (I estimate around 40-50 washes).  So I bought the same size and fit on Amazon just in a darker color to wear at work.  I also bought a pair of the 515 slim fit Levi's a few weeks ago and they were perfect and fit exactly the same as another pair I own.  But I wanted the less 'slim' fit of the 505s for work, also wanted the regular and not low rise waist.  So I ordered the same exact size and style:

Bad idea!

The 505s I got came with a tag saying 'sits below waist', which is NOT what they used to say.  Before, the 505s were a zipper fly version of the 501s.  Putting the pair of 505s I already owned next to the new pair from Amazon, I could see the crotch to waist was almost an inch shorter on the new pair.  Trying the new pair on, I discovered a most unpleasant sensation of my 'man parts' being crushed in agonizing ways.  No amount of tugging would get the pants to sit right.

Then I tried on the 515 slim jeans, and they were actually ROOMIER in the crotch area.  The thighs were a little slimmer than the 505s, but the seat was the main difference.  No sag in the seat of the 515s compared to the 505.

And then in trying on the recently purchased 515s (in the same color as the new 505s I purchased) I noticed something interesting.  The denim in the new pair was thinner and tougher feeling than in the 515s.  It wasn't just the feeling of the jeans prior to washing.  The 515s never felt that tough, and the denim was thicker in the side by side comparison.

I returned them based on a misleading product description (no mention of low rise waist) and inferior quality.  I gave the 515s a 5 star rating because they were as good as the previous 515s that I bought at a high price from a department store.  The previous 505s were also great (Fred Meyer of all places - though they don't have the 505s anymore... booo).  So I'm sticking with the 515s until something changes with them.  I'll take the slightly low waist and save my manhood.  And the better quality denim means they'll last longer anyway.  So here are my comparisons:

Levi's 505 purchased 9/10/12 from Amazon - 1 star
Levi's 505 purchased fall 2011 from Fred Meyer - 5 star
Levi's 515 purchased 6/22/2012 from Amazon - 5 star

Just be aware that the product might differ slightly from what is described, and that the quality appears to vary from order to order.  I suspect that is why the great divide in 1 and 5 star reviews.  I love Levi's jeans, and I will continue to buy them, but I will be a little more careful with the online purchasing.  And remember, if you buy from Amazon, they will return or exchange any unwashed clothing items.