Everyone seems to think this can lose you a sale, but I think it's important to note that all the adsense does is inform your customers about the competition. You won't lose the sale if you're clearly better than your competition. So, be better than the competition, run ads, and make more money overall. If your business depends on your customers not finding out anything about your competition, you're kinda ripping them off in the first place.
Since I posted my original comment where I said I thought it was probably a bad idea I have read some of the posts pointing out the other side of the argument and have been quite impressed. My own "personal" experince is that it was poor business for me. One of my sites sales tripled when I removed adsense but I accept this could be different by site/topic/product. It would be quite easy to compare the two. Try one month with and one month without (the longer you can try the more accurate the results are likely to be) and see which creates the highest total revenue. For this exercise to be "accurate" (within reasonable margins) you would need to have stable visitor numbers (i.e. similar in both periods) and also a fairly stable CPC on the ads that would show. If one or both of these fluctuates then a longer trial period, or more lots of one on one off, would probably be better. Whetever you decide I would still suggest you turn the "Online Advertiser" option OFF in your google CP to prevent your direct competitors deliberately targetting their ads on your site.