Metaproducts OE does _not_ use a propriatory browser.  The 
downloaded websites care fully usable in IE, Netscape 
etc.  It gives you the option of converting URLs to local 
for each project you create.  The updates to previously 
downloaded sites is fast and accurate and the projects 
file sizes are minimal.  It can use about 3 different 
methods to varify that a file has been changed on the 
server, including date, size, content and changed status.  
Try downloading the trial and having a play with it, it's 
the best downloader I've ever tried, it just costs to much.

Tom