Chitika, a search-targeted advertising network who serves over 2 billion ads a month (thanks Wikipedia!), has their December results in where they parse down traffic by operating systems. The results? Windows Phone 7 did grow from 0.4% to 0.44%.
Yeesh. While technically improvement with the holiday season behind us we would have expected a sharper, more significant rise in reported traffic. Now granted, Chitika's numbers are but one ad-provider and probably don't tell the whole story (lots of factors at play here), but had the number jumped to 1% we'd probably be reporting it as positive too, so to be fair... They finally conclude with:
It’s still got a long way to go, and it’s nowhere near a threat to Android and iPhone yet, but it is growing.
For anecdotal results, TheNextWeb took a look at their traffic and found that WP7 is growing and doing pretty well, considering the competition:
I took a look into our traffic numbers here at TNW, and it seems that, at least from our vantage point, Windows Phone 7 is in fact growing much more rapidly than what Chitika reports.
They note that being a tech site, their numbers are pretty skewed, but it goes to show that Chitika's numbers are but one way of looking at these things.