First, yes, Redfin agents don't get commissions the way traditional real estates agents get commissions. However, Redfin agents do still want to close as many deals as possible. Also, while real estate agents have a tough job finding good leads (especially given that leads don't exactly keep buying property) Redfin agents do not have a tough time finding leads (they have one phenomenal website that just gives them constant leads). What it results in is that a good traditional agent will put in a lot more work to find an appropriate place for you, because not only do they rely on you buying through them, but more importantly, they rely on you being happy enough that you recommend them to other people.
Redfin does not need your recommendations, as they've got a line out the door. So if anything starts getting difficult with your purchase, Redfin has no incentive to stick around and figure it out.
I've bought three properties and made an offer that fell through on one, and looked around other times. I've tried both traditional agents and a Redfin agent, and will never again work with Redfin.
I think in situations where the property doesn’t have any issues, where you’re just going in to buy a place, they can work out fine. Unfortunately you have no idea what kind of place you’re looking at until you’re trying to buy it.
Every worthwhile agent will have a ton of useful information before and after you purchase.