Cuil lacks the "Wow!" factor that Google had when it first started.
Google was truly revelutionary - it was so much better than other major search engines of the time; Altavista back then was decent, but its interface was heavyweight (also parts of it were paid subscription from what I recall) compared to Google, which had a more frequently updated index, loaded super fast, and focused on doing one thing very well - search!
Cuil comes across to me as a Google clone with columns and images...
The image part is badly implemented, because often they're irrelevant to the sites they're associated with, plus they appear to load remotely (hotlinked!), which is a bad thing in regards to security, privacy, and performance - loading of 3rd party images slows things down. Google understands this and caches everything it possibly can - they've taken some flak for storing copies of thumbnails, but they know that performance is what people expect ... the Cuil folks don't get it
Also, the back button appears to be disabled at times on Cuil, and also the Previous / Next buttons are poorly positioned / awkward to use.
Finally, unless Cuil search results are exceptional, which doesn't appear to be the case from what I've seen so far, all Google has to do is simply add a column layout and toss in some thumbnail images, and they'll basically make Cuil redundent.
Ron