"Warlands: Ice Age" used this lettering technique too. I can't find any sequentials online, just covers.
I remember being impressed by it when I first saw it, but more so for the idea of it. It's good that people are trying this stuff, but I think if it was effective it would have become more widespread.
In my opinion, when reading a comic your brain subconsciously fills in the blanks behind the balloons and, as long as the lettering is good, you don't really "see" the lettering. Much like how you can forget that you are reading subtitles on a film after a while.
When the covered art is semi-visible and blurred you are more conscious of it and I find that I automatically, and again somewhat subconsciously, try to imagine what the uncovered art looks like instead of getting on with reading the comic and appreciating the important unobscured artwork.
