The reviews on Amazon are very positive, it sounds like the most major change is that the illustrations have been updated. For the money you may as well get the most up to date information.

Here is a link that might be useful: Amazon Reviews

I purchased the new edition --owned the old one and bought a new one because I figured there would be changes - There aren't any-- NONE except the cover art. My suggestion-- go online and buy an old copy for a couple of dollars, used and don't waste the money on the new one!

I got the 1981 edition yesterday at a thrift store for 1 buck-o-lo.
Been looking at it instead of working. heh heh heh.

I do not know whether any of this would be useful. I bought "Cash from SFG" together with the 2005 edition of SFG in February. Since the latter book was still unavailable, Cash from SFG arrived first. I read through it, and tried my hand in SFG. It is only when the 2005 edition of SFG arrived that I realised how valuable this book really is. Of course on the SFG website, there are improvements posted (no more digging, Mels mix, etc), which is very useful!!

In this sense, the 2005 edtition is proving to be worth the while.