It takes up 18 megs of ram, as opposed to the nine-something of Netscape 4.x. And it loads very slowly, compared to IE 5.x. Finally, I'd add to all this that the IE-3-ish interface is visually a disaster.
Personally, for me it is faster than Nestcape Navigator (most recent version), uses less memory, more stable than any Netscape in memory, and slightly better output than IE (which IMHO, has much better output than any Netscape in existance)
This browser uses only about 12-16 megs of ram on my machine, and it loads incredibly fast, too. I double click on the image and the browser is there instantly. It gets there faster than the Windows Explorer. IE 5.5 takes 2-3 times as long, and if you use it for more than half an hour, it's taking up a good 13+ megs anyway. I've actually seen IEXPLORE.EXE take up over 25 megs on my machine once. Also, this k-meleon browser is considerably more stable than any other browser I have ever used.