Have you tried a Google search for Windows 7 recently? Apple is running ad copy targeted at Windows 7 searchers using Google Adwords. They have taken thier head to head Apple vs. Mac strategy and extended it to SEM in a fairly direct manner.
Personally I would go more tongue in cheek to be in line with some of the more agressive Mac Vs. Windows ads that we seen from Apple:
Upgrading to Windows 7 ?
Switch to a Mac and
Save yourself from pain
Search Engine Marketing and Content Targeting are great ways to target searchers and surfers who are part of your target market but are actively evaluating your competitor’s products . These surfers are often in-market for your class of product and are low hanging fruit that you should be actively targeting with your messages.
Your ad copy should call out your strategic advantages and can also play on the pain points of your competitor’s products. Just remember that in most cases you can bid on your competitors branded terms but Google does not allow you to include those branded terms in your ad copy. Apple may have gotten away with this due to the fact that people are allowed to bid on “Windows” since restricting it would be undue hardship on unrelated businesses such as home window manufacturers and installers.