I'm a huge space buff, and at nearly 44, I've just discovered this flick for the first time. I came at it in a roundabout way from Space 1999, then UFO. I went hunting for other Anderson creations and found this was their first live-action work. What a home run! I actually heard about this movie many years ago, but never knew what it was called, so I'm happy to have found it by accident.
These Andersons were nothing short of amazing in their writing, the execution of the completely believable and realistic-looking models, the quality of acting, etc.
I don't think it looks dated at all. Let me tell you... I'll take good old models over the fake-looking CGI crap of today ANY TIME! Seriously, most of the rocket scenes looked pretty real. They had it down to a science! If you choose to think of what you are looking at as real, it isn't hard to actually believe it.
Also, the amount of detail in set designs, the beautiful photography, the whole look... man, I wish I could go back to that time! They knew how to make great movies in the 60's. Personally, I've lost all interest in Hollywood movies today. Anybody with a budget can do CGI. I hate it! Bring back the models! Think of all the people that style employed! Anyway, I am ranting. :-) If you like good sci-fi that's very well-done, you will do yourself a service by watching this.