I'm a Realtor, so let me give you a real world example, and you can decide for yourself.
There are hundreds, and often thousands of properties in a given area. When I get a new client, I spend time asking for parameters (bedrooms, baths, amenities, price etc). From there, I do an initial MLS search. MLS usually beats realtor.com and many of the other sites by a couple of days, because we've got live data.
From there, I take you on an initial outing where we look at five or six properties. I use this as a chance to learn very specifically your likes/dislikes.
From there, I scour the MLS and start sorting through. Then, while you're at your job, I PREVIEW these properties, and weed out the ones I know you won't like.
Usually, I only have to show 8-10 ten homes to get one you really like. Sometimes more, but if we communicate well and I 'get' what you're looking for, we usually find it. WITHOUT your having to drag through 30+ house (and believe me that gets old fast).
Not only that, I help you negotiate. I do this every day. So I know HOW to do this, and effectively.
Also, for new construction...consider this. If you show up with a Realtor, think about how they really try to get our business. They know we always have buyers, so they have a seperate marketing budget to take care of us. We get a better deal than you just wallking up probably 9 out of 10 times. They (the builders) understand that having a relationship that benefits them over and over again is better than the one time walk up. Some people mistakenly believe that the builder will cut the price by 6% to save the commission and pass it on to you. That simply isn't the case. (I've had a friend brag about the $10,000 he negotiated a builder down, when I had the same builder call me a week prior saying they were offering $30,000 in buyer incentives).
So, to answer your question, yes. You'll save a lot of time AND money getting a Realtor to represent you!
Good luck in your home search. If you need any additional help, feel free to contact me at rodbaker@fwrealtor.com.