I echo Lord of the Rings' sentiments - basically $18 is not a lot of money and, on top of a noticeable connection improvement and the word Turbo-Charged in reassuringly large letters below your hyperspeed, mint blue connection bar, you also get a warm glow knowing that, despite your natural disinclination to pay for stuff, you have actually helped with the development of a very useful product.
I haven't found files roaring into my shared folder since upgrading, but they do at least canter rather than waddle these days.
I also had a few probs with the latest version for OsX but they got schmooved out when I went to an older version. If it ain't broke...