This was my first Birkenstock purchase and I am not disappointed.  The size conversion was spot on for me.  They are very comfortable and the design of the foot bed provides good support in all the right places.  I was worried that the cork would be unforgiving when walking (e.g., very stiff and unyielding), but they are not.  The top straps are adjustable, which is nice.  I wore these with wool socks but plan to wear them without socks when the weather warms up a bit and I still have room to adjust them down to compensate for that.  Overall, I would highly recommend these shoes.