do they typically run larger or smaller compared to US shoes sizes?

They are Euro sized which makes it a little hard to compare directly to US sizes. But they do run quite narrow unless you get the Mega width and even then they are fairly narrow.

My experience, larger. For example, I wear a 9.5-10 US and 10.5 w/ Sidi.
Also, I found that the Sidi's cut off my circulation and was having hurting toes at the end of long rides.

Now I wear the top-of-the-line Specialized and they're lighter and more comfortable than my more expensive Sidi's. But hey, everybody's different so Sidi's may be perfect for you.

If you're going to drop a few Benjamins on shoes, best to try them on first. I see a trip to your LBS in your future.

Yes I agree with not2blu.

I am a US size a 11 sneaker, and got size 44 EU sidis (11 US on a conversion chart). These were slightly too small and I ended up with a 45 sidi. I would say bump up one size, but definately try them on before you buy.

I wear a US size 11 & wear 45.5 Sidi's. Their shoes have a much smaller toe box than the Shimano, Specialized or Pearl Izumi shoes I've worn. Try before you buy.

I wear U.S. 'joggers' size 10 to 10.5, and my Sidis are 43

Sidis stretch a LOT!

Sidi's do stretch a lot. Back in the 80's, we bought extremely tight Sidis. Soak them in water, wear them all day at home so it molds to your feet. Got to get them extra tight. I see now, there is actually a shoe company that does the same thing but put them in the oven or something? Same concept.
I use my Sidi size as my baseline. I wear a 39 cause I don't want any slippage on the pull up (you are not walking on them). But if I was to buy a sneaker, its a size 42.
I'm always surprised to see people see if there is room in the toe when buying cycling shoes.

You can't really buy the right size without trying them first. With something as expensive, and as influential on your riding comfort, it doesn't pay to leave it to chance.

By the way, I have a pretty wide foot, and I've found the "mega" to be just the right width.

I found this to be the same for me. 44 for all the other brands I tried on but the 45 Sidi felt the best out of the box, so that's what I went with.

need to swing by the LBS either today or tomorrow to try on a few pair of Sidis....

Performance has them to try on. You really need to buy the first pair at a LBS, since they are difficult to fit based on charts.

i think Plano Cycling may have them as well.............

That would be them running smaller, not larger