My personal conclusion thanks to my own experience with z88dk and SDCC was that SDCC produced much better code than z88dk. Today I got confirmation from one of the z88dk authors here : "sdcc currently generates code which in general is smaller and faster than the one generated by z88dk [...] it does support a more complete subset of standard C compared to z88dk. It is actively maintained (releases about once a year) and keeps improving.". Don't get me wrong : competition is good and actually benefits to both projects. Still - basically it's a fact that today SDCC is the best C compiler available for Z80 developments.
The day of new www.norecess.net announcement, this site has been advertised to 20 personal contacts (related to CPC) and few websites : CPCRulez (french), PhenixInformatique (french) and CPCWiki (english).
For the fun, I just checked the stats of the website and found out that 548 unique visitors went to this site on January, 5th ! In the context of "dead" machine that Amstrad CPC is, I consider this as an awesome hit count.