I’ve tried other search services, but I always end up back at Google, because the search results are consistently better. Google does collect information about its users, and uses that information to target advertising. Google also looks at the content of GMail messages for the same reason. If that bothers you, there are ways to prevent it, or you can stop using Google’s products and services.
That said, in all my years of using Google’s services, I’ve never encountered anything that made me want to stop using them. Google does occasionally annoy me by dropping services like Reader, and Google’s advertising is ridiculously overpriced, but on balance the company provides far more benefit than any potential harm.
For example, Google spends enormous amounts of time and resources on making the web safer for everyone. Much of that effort goes unheralded, but occasionally we catch glimpses in the form of blog posts, like this one, describing recent improvements to GMail security. Compare that with Yahoo’s recent track record, which clearly shows that user security and privacy are not a priority at that company.