I called it a "toy" because in my opinion, a filter is a tool to weed out baddies like bacteria and protozoa (cysts, crypto) -- and anything that can't do that reliably is not worthy of the name -- and thus, a toy. I may be overly harsh though...
But I agree that it can be used in conjunction with something else -- such as chemical treatments. In theory, one can first treat the water with chemicals like chlorine dioxide to kill viruses and bacteria (let chemicals do what they do best) -- then take care of the harder-to-kill stuff like protozoa (crypto) by filtering. However, the 3.0 micron size is still 50% BIGGER than the size of smaller protozoa -- which start at 2.0 micron! So again, is it still a false sense of security for the times when you truly need the filter?
The Seychelle in-line filter is just an ounce plus a few dollars more than the AQ Frontier Pro. I also don't see using this as a stand alone, but rather in conjunction with chemicals. Once the water is chemically treated against bacteria and viruses, the Seychelle's smaller pore size (2.0 micron) is sized appropriately to protect against protozoa.
Warning: Self Promotion -
If anyone is interested in getting a Seychelle for cheap to try it out, please click here for a lightly used one as well as an extra brand new, still shrink-wrapped filter element.