It's a neutral-moderate overpronator shoe. For me it feels a bit weird since I'm a midfoot striker, and this shoe is totally planned for heel strikers (you'd understand what I mean immediately once putting it on your foot).

Sizing is very small, very tight especially at the toes!
I'd say definitely go 1 or even 1.5 size above your Nimbus size. My Mizuno (prophecy) size is US11.5 and the Cirrus33 size is US12.5. Which's actually the first time ever I needed a US12.5 size!

UPDATE: Even US 12.5 is a bit too small for me (with orthotics). I don't know if I'm going to try size 13 (for the 1st time in my life) since it's pretty frustrating this shoe is hell narrow. I don't know why asics did that. It's a shame, such a good shoe with such weird sizing.
Asics should provide EE width for this style, the current width is ridiculously narrow.