We have a Mac OS X application and we'd like to use AdWords to help people hear about it. The two tests we've done have produced 70%+ of our traffic coming from IE and then Google downgrades our keywords because such a large percentage don't convert and so Google assumes it means the keywords are bad.
This despite our ad clearly saying "for Mac OS X" - I don't know if IE people just don't read and click on ads randomly, or if this indicates that Google (or someone else) is messing with AdWords clicks via scripts (which would be really bad for the viability of AdWords in general), or what.
It's hard to imagine that people are clicking on a link for a Mac OS X only product while running a windows computer - yes, there will be some small percentage of such who have a Mac at home or something, but not 100% of them!
I need some way to say "only show these AdWords to people who are on a Mac!"
I tried "Topics" and indicated yes for Mac OS and NO for Windows OS. No improvement.
I spoke to Google AdWords reps about this and the answer they suggest is to put Mac OS X in the ad by getting permission from Apple legal to use their trademark like this.
Try to find your user base location and limit your ads according to countries. May be you are running your ads across the globe and your budget is getting consumed quickly. (There are certain regions where people are quite reluctant to buy anything online) In case you wish, you can also filter ads based on demography (age of users, gender)
Also, I don't think they provide filters based on OS as of now but yes that is a very often requested feature by the community. They do have filters based on platforms (mobile phones, desktops/laptops)
By the way, as far as my knowledge goes, Google will NEVER lower the Quality Score (QS) of your ads based upon YOUR conversion rates. Their job is done as soon as someone arrives on your page. They are concerned about whether your ads are getting enough clicks in proportion to impressions (CTR), whether you have a nice and fast loading landing page, whether keywords are matching your ads etc.