The last several posts seem to be arguing for a conical, without realizing that they are. You can in essence do a primary and secondary fermentation without racking to a second vessel, which was always a concern for me in the past. The "neck" opening is about 6" which is plenty for anything short of a football which you might desire to stuff in there. And even the faulty ones seal up better than a bucket. I don't think that the cost is all that significant compared to a bucket which is specifically sold as a fermenter, but we all have different financial situations.
The only serious downside I have encountered is the vertical dimension, a carboy or bucket will fit into a much shorter space than one of those damned tall conicals. Also you can't see what's going on inside the fermenter as well as you could with glass [yes, I too enjoyed the lava lamp comment]. Just so you don't get the impression I'm on the payroll of the manufacturer, there are a number of things I would very much like to see them spend a few bucks improving. A clear viewport in the lid to monitor the process, better seals at the lid to body and the ferm-loc hole, altering the casting mold so the thermometer shaft is parallel to the ground rather than perpendicular to the angle of the fermenter wall, clear trub balls, and an option for a smaller trub ball are the ones I'd most like to see. I'm not holding my breath while waiting for the manufacturer to do the right thing and improve their product. Sooner or later though, if they don't someone else will.
One of the other posters mentioned that he had problems with the conical plugging up. I haven't encountered that problem - yet. This morning I finally remembered to dump the trub ball on a batch of stout - about 3 days late. The ball was completely full of yeast sediment [a first] and there was about 3 1/2 " of additional sediment in the bottom of the cone. I removed, dumped, sanitized, and replaced the trub ball, opened the valve at the bottom of the cone, and after a few healthy "glugs" all the yeast sediment in the bottom of the cone moved into it's new quarters in the junk ball.
I have minor issues with the Fast Ferment units and would go with another brand in a hot second if a better option becomes available, because I think FF has gone low budget on a few things, but at the moment you couldn't pay me enough to go back to buckets or switch to carboys.