MLS Search vs. Finding Your Agent

This is a post that is dedicated to what might be the current real estate version of the chicken and egg question. I work in the San Francico market, so I'll be using my local multiple listing service, the San Francisco MLS to illustrate my examples. 

San Francisco is a real estate market in which individual agents compete for the right to exclusively represent a seller, but then market those properties in a cooperative MLS. This means that any agent from a member brokerage (basically, any reputable firm in town) in San Francisco will have access to all properties listed for sale in San Francisco, regardless of their own brokerage. 

There are a few exceptions to this - most new construction projects list only some of their homes in the MLS, not all of them. In addition, our Mayor's Office of Housing has some housing programs that will have resales that are often only listed on the mayor's website. Finally, even SF has a small number of FSBO's (for sale by owner), and these are generally not in our MLS. 

Depending on the time of year, there are roughly between 1,500 and 2,500 homes listed for sale in the San Francisco MLS. While your requirements will obviously narrow that number down a lot, that is a lot of data to sort and sift through. One of the things a great buyer's agent will do for you is to help narrow that data into a manageable amount but many home searchers today often begin searching for homes before they begin looking for an agent.

As a home buyer, what are your favorites websites to search for homes in SF? What features of those sites are most important? Is it more valuable to have a great interface for search, or are you more concerned with being able to store, sort, and share information about the homes that you like? Do you just sign up for an account at the first MLS search site you find, or do you spend time actively researching tools to search for homes in San Francisco (now that's getting meta, isn't it!?)

Are the tools that an individual agent offers you for searching the MLS important in your selection of a Realtor, or do you consider the MLS search tool and the Realtor to be a-la-carte items that you mix and match to best suit your preferences and needs? I'd love to hear your thoughts!