I hear a lot that comparing massive trees with Razl takes awhile. Well, it does have to crawl your entire, and I mean entire, Sitecore tree to show you all the differences right down to the versioning. Sean Holmesby came up with this neat trick to help speed this up.
In Sean's tip, he opens his local Sitecore instance to the areas of the tree he knows he wants to move. He then opens the second instance and does the bulk move. This avoids the scenario in which the second instance of Sitecore needs to keep up with your local and bogs down the process. By doing this you can effectively work on other things all the while merging large parts of code.
This is a neat trick that will dramatically speed up your process. Try it out and tell me how it goes!