IMO it's probably too new to rate, and given the number of failed queries I'd have to give it several more tries to have a fair opinion. A lot of the responses from the peanut gallery are pretty negative. Whatever -- I think this is probably a case of "all press is good press".
Some of the comments I found particularly interesting, though, are those berating Cuil for
1) choosing a non-english domain name and
2) allegations that they weren't smart enough to research that transposing the "i" and "l" will take you to a porn site.
IMO if this was intentional, it was actually kinda genius.
By way of illustration, I never had a reason to visit the official site of the White House online. But, had that day ever happened, I was well-versed -- thanks to the cult anecdote of folks who accidentally point to whitehouse.com instead of whitehouse.gov -- that the former was a porn site, while the latter is the current residence of GDubya.
Granted, because it's not English, Cuil is not as in-the-face as say the "FCUK" brand of clothing, but for whatever small percentage of folks mis-typing the domain that end up on culi.com, I'm pretty sure they'll remember how to spell it the second go around. That sequence has a much better chance at brand stickiness than, say, Kaango or Loopt, methinks.
My advice to Cuil is that they should pay whatever the domain-squatters on ciul.com are asking and put a Goatse pic, stat!