Well, for what it's worth, I have a four-slinky doublet stretched about 33 feet, end-to-end, in my attic, and have had good results with it on 80, 40, 30, and 20 meters. I feed it with 300-ohm open twin-lead (insulated, but with openings, so it is kind of like a cross between ordinary flat wire, and ladder-line), coming out of an MFC VersaTuner II. No idea what the mismatch between the feedline and the antenna is; I assume it's probably horrible. Regardless, I've worked SSB from here in Virginia to Italy (the other guy had a world-class antenna array, however), and both CW and SSB all over the continental US. Judging from my contacts, it would appear to radiate off the sides on 20, off the ends on 40, and every which way on 80. But that's just a guess and might reflect more about when I operate those bands than anything else.
With 100 watts from my Yaesu FT-897 (and from a Kenwood TS-430 before that), I tend to get a lot of S6-S7 reports on both modes within 1000 miles, when conditions are good. Out towards the west coast, about 2000 miles, I hear more S5-S6. Not going to win any contests with this thing, but it was cheap, easy to construct, covers several bands, and actually works.