I'd say so. The difference in performance is pretty remarkable.
Some stuff won't change. Black won't get blacker. Other stuff will change quite dramatically. If it's calibrated properly then it will get a lot quieter than how it is out of the box. Brightness will drop a little, but video contrast will appear to be higher. Bright and intense colours will really pop out.
Then there's the more subtle stuff: the first thing is that the picture seems easier to watch. That's from a combination of factors; better motion, more realistic colours, truer skin tones. Your mind isn't having to work as hard to tell you that this is the image of a real person, or those are buildings and trees. Everything is more natural so your mind relaxes in to accepting the picture as real.
Improvements in the colour fidelity and getting rid of the over-sharpening then allows the real picture detail to come through. You start to notice a much bigger colour palette and that means subtle differences in colour shades that were previously all blended together are now properly displayed. It creates a greater sense of image depth and individual items appear better defined from each other, so the picture looks to have more detail.
It generally takes about an hour to really start to pick out the differences. The next two or three days viewing are where you'll find yourself playing clips of movies you though you knew but now they look different. After that you'll look at other peoples TV images and wonder how they live with the picture.
If you're in Essex then have a word with Gordon Fraser at Convergent AV. He's one of the few people in the UK other than me who I'd trust to calibrate well.