like Jeff above, i came to Sidi from bicycle cleat usage.
when it was time to get serious about moto boots Sidi was a natural choice: Disco's with the hard gum rubber sole and big latches. Bought June 2003 from Motonation for a hair under $300, and i still wear them every day. Size 44 and my normal shoe is US 10. I have to wear double socks, but i do that anyway (wicking New Balance stockings w/ Woolrich).
They are waterproof when it is not raining, when it rains they are flip-flops
(this was before the customer onslaught of complaints prompted Sidi to re-brand them as 'Discovery-Rain'
Mine have needed cobblering 2x for disintegrating stitches where the tongue meets the upper, and as of now the stitching around the plastic exterior heel cups is gone, and i finally wore through the shift pad on the left boot last month. I'll get a new pair of boots (likely Force etc w/ the dirt sole) and get these Discos refurbed. I wear A-stars Tech stuff in the dirt for now, but the Force series may replace them.
The Discos have 6 years and untold walk/ride miles in them-- they're waaay too floppy for any dirt use now, but still OK for commuting/street. Once refurbed they'll be good for another 6 i'll bet. Talk about value-for-money
I'm def w/ Annie: it's dirt/DS boots for me 24/7/365 no matter what profile i'm riding. I'm too used to the support and rigidity now that a street boot just feels like Chuck Taylors now. After yesterday's gravel lowside i'm loving my Discos all the more.