Well it uses the same deflate algorithm which is used by zlib, gzip etc. There are many much more capable compression algorithms which will get much better res

Well it uses the same deflate algorithm which is used by zlib, gzip etc. There are many much more capable compression algorithms which will get much better results with alot less cpu time (lzma comes to mind), however the big deal is that deflate is supported by all browsers and thus it is a standarized means of compressing content. With that, being able to squeeze out 3-8% more compression for compressed web content can likely be attractive if it is a decent part of your bandwidth usage.