I have two MagBloks, and they look very nice. But they have yet to be installed, because I bought them to go in the 'new' kitchen, and now it turns out we do all the prep on the islands and there are no good places within reasonable reach to install them. So we're keeping an old Wusthof block -- which holds a pretty good collection of knives -- and I will need to talk to BoardSmith about getting a custom block for the 'above 240' blades I have started to accumulate thanks to web sites like this one.
When the JKS mag racks were first posted I thought they were a bit too expensive relative to MagBloks, but when I saw them first hand at the ECG I was able to appreciate how much longer and taller they were. But from a practical perspective, there aren't a lot of open wall spaces in a lot of kitchens for the longer racks. They 'work' where there are no upper cabinets (assuming a wide enough wall), but if you have to put one below an upper cabinet it would be hard to keep from at least partially blocking with the typical crap most people have on the countertops.