Sadly I haven't tried one, but in videos signature Marshalls (Malmsteen, King, Satriani) sound really good. But that's only videos, so I don't know how much that's worth.
I have a Satriani delay and Zakk Wylde chorus which are pretty good, but I'm a very casual FX user and can't tell you how well they compare to great non-signature pedals. All I know is they're better than the cheaper ones I tried (and much better than the ones in my Boss multieffect).
As for guitars, Gibson Tony Iommi signature (the only guitarist in this post I actually care about), my own Jackson DK6 Christian Olde Wolbers (Fear Factory):
...annnnnnd...
Squier Avril Lavigne Telecaster. Seriously, I like it. It was cheap, and if I'm lucky, I'll get one on eBay some day. Put a Black Winter into it, and bam!
Squier Avril Lavigne Telecaster. Seriously, I like it. It was cheap, and if I'm lucky, I'll get one on eBay some day. Put a Black Winter into it, and bam!