The ffmpeg devs have said many times in public that they routinely get speedups of 10x or more over C code. I'm not a reputable source on this myself but I highly recommend looking into their channels, mails, or posts.
I already read PCL and imho it's a really great book. In case, however, you have further questions (like I did) have a look at #lisp on irc.freenode.org - the guys there are really nice and helpful.
The ffmpeg devs have said many times in public that they routinely get speedups of 10x or more over C code. I'm not a reputable source on this myself but I highly recommend looking into their channels, mails, or posts.
I already read PCL and imho it's a really great book. In case, however, you have further questions (like I did) have a look at #lisp on irc.freenode.org - the guys there are really nice and helpful.