It's a classic and you pretty much have to do it. It's the quintessential Vegas photo op!
And it's way improved. I remember back in the day when there was no parking lot and tourists would try and run across Vegas Blvd. to see it and get a photo in front of it. Ahhh, those were the days. But we've made it all tourist friendly now.
When the parking lot isn't full, you can conveniently pull in, park, and wait in line to get your picture taken. This isn't a professional photo place, so bring your own camera and don't give anyone money just to take your picture. It's usually not difficult to find a friendly person to snap your photo for you. And sometimes you will luck out and there will be an Elvis impersonator or Big Bird or whatever standing around and they'll take a photo in front of the sign with you (for a generous tip, of course).
So yeah, don't just drive by it, pull in and stop. No Vegas vacay is complete without a photo in front of the famous sign.