Unsurprisingly, I don't find myself making gender-based assumptions much at all. I say "unsurprisingly", since my head of department is a woman, and a very successful head of department at that. As a department, we have about a 3 to 1 split, so the ladies are certainly outnumbered, but that reflects the ratio of applicants' genders rather than any hiring policy.

I do tend to find, though, that there are specific gender differences that have a bearing on someone's work in IT. Some of the more brilliant technological successes I've seen in-house have been related to the male inclination to (as has already been mentioned) become interested to an almost obsessive degree, and concentrate to the expense of other work. Flip side is that some of the more spectacular failures I've seen in house have also been attributable to men, for much the same reason.

On the other hand, the women in the department tend to be a rather more pragmatic group, and their ability to multitask means many of the most successful projects have been kept on track and properly managed by them. They're also generally less blinded by the latest whizz-bangs, so the solutions they pick tend to be both simpler and more stable.

I realise these are sweeping generalisations, and that there are huge variations within each sex, but men and women are not the same. They each have different strengths and weaknesses as groups as well as individually, and the best teams IMHO recognise this. Overall, though, I've not yet found any difference that makes me feel one gender or other is overall better suited to IT than the other.