well, the results are in.
i used McCormick brand vodka as my cheap bottle, and stoli as my control. I ran the McCormick through a brand new brita 6 times just to be sure, and put it in the freezer along with some unfiltered McCormick's and the stoli.
all taste tests done with raw shots, poured in different shot glasses by my gf (w/o me seeing, if i really need to state the obvious).
first test was unfiltered mccormick's vs. filtered. the filtration did make a difference, i easily distinguished which was filtered. so it definitely does make a difference on taste. i think someone here said it wouldn't. go test it if you don't believe, it is a notable difference.
second test was, naturally, the six-time filtered McCormicks v. Stoli. UNFORTUNATELY, stoli was the winner. i easily distinguished which was filtered mccormicks and which was stoli (i'm not avodka drinker, so this wasn't easily distinguished because i knew stoli's taste or anything).
so, it does get stuff out, but not as much as you'd like. I am considering attempting further filtration, but i must say that it definitely makes it drinkable. and a brita filter unit, w/ a filter in it already, cost me 14$ at walmart. i spent low 20's after my vodka and brita, which made plenty of human-grade vodka.
totally a worthwhile project, but don't expect grey goose. (i'm sure once i attempt infusing it with flavors it will be an even more worthwhile project)