The results when searching in blinkx and Youtube appeared to be quite different. This seems to be because in blinkx you can specify the exact providers you want, eg CNN, BBC etc, and get a correspondingly smaller set of results. Of course you can also search through all the listed providers, giving a much larger number of results, but it is good to have the option, and it helps to be able to search your preferred sites without having to go into each site separately, while at the same time also honing in directly on to the type of media you require. Youtube seems to be more generalised, with a more random and collaborative approach to sharing videos. It depends on the type of search you want to do and the reason for it. Youtube is more of a social thing while blinkx is more of an information provider, more 'serious' and practical.
The magazine option in Google Books could be useful for previewing a new magazine, getting an idea of its contents, style, relevance etc. I had a look at Ancestry magazine, and it seemed that the latest issue displayed was January/February 2009, so evidently you can't read it here in lieu of paying for a subscription if you want the most up to date issues, but for back issues it does appear to be most useful. I like the Overview section which gives a short precis of the magazine, allows you to browse issues and also gives a cloud tag of common terms and phrases, and even a map of places mentioned (although this seems to be restricted to North America so not especially relevant to people in our part of the world). I'm not sure how useful the magazine option would be for finding specific articles but I can see possibilities for serials librarians looking for magazines on a certain subject, or reference staff helping patrons find the same. From what I've seen the book search appears more directly useful, especially if full text is available, and key word searching allows fuller access to a book's contents than an index can provide.