I used a buyer's agent a few years ago, and have had experiences on behalf of clients with a number more. I had a very good experience and whilst they weren't able to add too much with property searching, their assistance with property evaluation, price expectation and value, and dealing with selling agents was fantastic.
The thing I usually tell my friends is that selling agents sell property all the time, whereas buyers very rarely buy, so there is a huge imbalance in expertise and knowledge. A good buyers agent evens that up and cuts through a lot of the BS.
I did shop around though before choosing my buyer's agent and I met with and got proposals from a number of buyer's agents who I did not feel comfortable with and who it was clear were only in it for their own gains.