zappos.com carries a number of Inov8 models and they provide sizing advisories, presumably because of customer feedback (but I don't KNOW that).
Example, for one model:
Please select a half size up as this shoe runs a half size small. (If you wear a Men's size 9, please choose a Men's size 9.5. If you wear a Women's 8, please select a Women's size 8.5.)
They say that for SOME Inov8's but not all.