I think they're a great addition with either a professional calibration or you learning to drive it yourself (depending on how you are inclined).
If you look through display reviews many will tell you that, for example, when calibrated they managed dE (a measure of colour difference) of less than 3 for most of the gamut, which is claimed to be at the threshold of vision. I dispute that as I can very easily see by eye colours (particularly greyscale) that are off by well under 2. (in fact, the whole idea of dE was that 1dE was a noticeable difference, no idea where 3 came from). It seems to me it is a blunt "rule of thumb" that doesn't apply equally to every part of the colour gamut.
3DLUT calibration - like you get in a Lumagen - is a given in the professional content production industries. They're using extremely high quality reference broadcast monitors, and even then they calibrate them with a 3DLUT. It is the only way to get a truly accurate colour volume.
To give you an idea; I'm by no means an expert calibrator but this is the kind of error distribution I can achieve by manual means using the controls built in to my JVC X30. The taller and further to the left the chart is, the better... Approx 30% of the measured points are between 1 and 3 dE.
And this is what I can achieve with a 3DLUT generated in Lightspace and loaded into my Lumagen 2143. No measured points above 1dE in this case (sometimes 1 or 2 are just over)
Don't get me wrong, the manual calibration does look good, but the 3DLUT looks much better to my mind. I'd go for accurate colour over resolution any day of the week.