Isn't the problem with Feedburner and RSS feed stats that they count "hits" and not actual subscribers (aka unique visitors). So if my RSS reader asks Feedburner 20 times a day for new content it counts as 20 to the total?
No. FeedBurner has a basketful of algorithms to deal with this.
In the most significant cases, the readers actually report back to FeedBurner how many subscribers are using that reader. For example, Google Reader. In the user agent string, Google Reader (as well as, I believe, Netvibes, Newsgator, and a few others) says "X subscribers", and that number is then used by FeedBurner. You can check this out yourself if you have access to web stats on a domain that hosts feeds. Check them out. You get to see the same numbers that FeedBurner puts on their charts.
With non-Web / non-centralized readers, it gets trickier, but FeedBurner uses IP addresses combined with user agent strings to get an idea of what's a unique reader requesting multiple times or not. Typically this system works well and isn't wildly inaccurate.
while i'm not certain, i'd like to think that feedburner is smarter than that and only counts uniques. however, i'm not familiar with the internals, and am only venturing a guess.
i do know that i've in the past used a WP plugin on a blog that definitely counted uniques.
Anyone with info on this want to clarify?