This study has an inherent flaw: the queries used were selected from the most common queries. Answering common queries is (relatively) easy, but Google claims (and other independent studies have shown) that Google is much much better than most of its competition for returning good results for uncommon queries (the "long tail" if you will).
Edit: I just (briefly) tested this myself. Searching for for my username on Gigablast returned 3 results: 2 of my HN comments and a wordlist. Google on the other hand found 3k results, with the top results being my linkedin and facebook profiles (which I would deem the "best results").
Can't agree more with that. I searched for some Cocoa part which was a tie between Google and Gigablast; a torrent which Gigablast could find, but at its origin; and the AD&D Sorcerer which Gigablast couldn't find anything about.
Gigablast might have better results for common queries, but those matter hardly to the typical HN user.
Edit: I just (briefly) tested this myself. Searching for for my username on Gigablast returned 3 results: 2 of my HN comments and a wordlist. Google on the other hand found 3k results, with the top results being my linkedin and facebook profiles (which I would deem the "best results").