Hello Luckypete, I use the Heiland LED on my Durst L1200. I have the B&W controler (not the splitgrade one) and the color controler. Will you be able to make better prints with it? maybe... Everything I do with the LEDs I could do it with my color dichroic head. But now I can do it much more smoothly.
About the contrast, I did some test prints from a stepwedge. I get the same contrast at 00 and 5 with both. The #2 I get from the LEDs is about the same as a #3 from my dichroic head.
About the light intensity. I can adjust it by 4 stops in .1 steps (from 0 to -40, not sure if it's the same on every LED source they make) . It's very convenient, you can change the size of a print without changing your lens aperture or the times, just the brightness factor.
About the ease of use. It's much more smooth to dodge/burn especially at different grades. I control the system (safe light, grades etc...) with one hand, I do the dodging or burning with the other and start the timer wit a foot pedal. A pure joy, I don't have to fiddle with the head filter dials between exposures anymore. If you are into splitgrade, it's also very easy. the 00 is just one click away from the 5.
On the L1200 it replaces the diffusion box (I don't know if it's the same for the M670). From time to time I wanted to print with my condenser head and had to remove the color one to put the condenser one...not very convenient! now I can leave my condenser head on the enlarger. The LED box takes the place of the condensers when I want to print with a diffusion light, and when I need a condenser and tungsten light, I just remove the LED box, put the condensers and use my condenser head as usual.
The illumination is perfectly even, border to border and obviously very stable in time. But that is also the case with my CLS501 color head.
Another very important point (for me!) it's silent...
Is it better than other LED systems? I don't know, that's the only one I used. Koraks build one himself, there is a great description of it on his web page. It looks very impressive, but it takes some time, effort, and quite a bit of talent to achieve a project like that!
Hope this helps