Yes yes yes!
This is LEGO. This is a castle. You build, you play, you build something else. And you get many figures to play with and to chose your hero from. (My favourite is the Maltese Knight.) The castle itself is nice with its four different sized towers, the drawbridge and the window in the rear tower. It's somewhat weird how it opens, though. You get two rows of walls by opening the walls.
The colour is not bad, but it doesn't fit well with subsequent castles, so I guess many people separate their Yellow Castle from their other castle buildings, maybe just using the figs. For me the Yellow Castle stands for its own as the cornerstone of Legoland Castle System rather than being part of the rest of the castleworld. It's the King of every LEGO Castle collection.
Well, I never had one when I was younger. But boy! was I eager for it when I discovered my deep love for LEGO Castle a few years ago! When I finally got my hands on my first (Yellow) Castle it was one of the best days in my entire AFOL-life :-)
One peculiar thing about this set is the presence of two blue 1x1 bricks and two blue 1x2 45° slopes that are not used when building the main model. On some pics of alternative models on the box you can see the blue parts built in:
Those blue pieces really are part of the set, they aren't just parts you had to add from your parts collection.
A second remarkable thing is the blue visor that is shown in some catalogue pics instead of the grey one. I've never seen one of them in real life and I wonder if it ever was released. Most likely it was just a part produced in small quantities for the fotos. I want one of them :-)
The third thing that is noteworthy is the pic in the centerfold of the instruction booklet, respectively in the first edition of the instructions. The pic shows how to open the castle at the hinges. Odd are the dark grey helmets the mounted knights are wearing. Those dark grey (Classic Space) helmets haven't been released as well. Besides this all the stickers seen in this pic are obviously hand-drawn.
Please take a look (sorry for the bad quality):
Fourthly, there have been three slightly different sticker sheets for this set, showing a move from dark shield colours in 1978 to brighter colours in 1982 (from left to right):
In the first edition the shields were of the same soft material as the visors.