Over time I reckon that 'single search' will replace 'metasearch' for general article access. This is not to say that there will not be target markets where niche databases do not continue to exist, rather that alternative solutions for general article searching seem inevitable given the difficulties of metasearch. Now, there is some discussion of libraries gathering and indexing data locally, and some examples. There will also be third party consolidating services.
In this context I was interested to be pointed by Wouter over het Web at the comparison [pdf] of Web of Science, Scopus and Google Scholar carried out at the University of Utrecht. This does a comparative review of features.
I was particularly interested to read that Google Scholar was better known than the other two in a survey of users.
Survey. A survey among 81 users shows that Scopus and WoS are less well-known than Google Scholar, but the results generated by Google Scholar are rated less highly, especially among research trainees/researchers, and among those, largely the scientific disciplines. Scopus is rated best in use, followed closely by Google Scholar. According to the respondents, WoS clearly has some ground to make up here. In terms of the relevance of the results, Scopus is likewise rated most highly of these three citation databases. [WoW! Wouter over het Web: Scopus reviewed and compared: the coverage and functionality of the citation database Scopus, including comparisons with Web of Science and GS]