it looks like the w5gi antenna, in it's full configuration is pretty big, 
though slightly smaller then a regular g5rv i suppose.
if it has stronger performance on 75 and 80, it'll be a better alternative 
to the g5rv, but it seems as though, with exception to the increased lobe 
performance, it might perform pretty much the same above 40M.
if it really does have more gain then that is also a plus...but that might 
be a bit hard to measure in real world application.
however, with increased lobe performance, I would think that one would be 
able to hear stations more strongly in directions you wouldn't necesarily be 
able to hear them as strongly with a regular dipole or g5rv antenna.
this definitely could be a plus for dx, but a minus for nulling out regional 
or short dx from the US/canada.
eitherway, it sounds like a fun and very easy to build antenna.  pretty 
forgiving as far as construction as well wich is nice.
and acording to the website, it doesn't necesarily require an antenna tuner 
to obtain a impedance match on all bands save 160.
73
Colin, V A6BKX