Hello Jools,
I think the general reaction has been that it is the best AP Paizo have done [not by a long way or anything as the general quality of almost all the APs has been very good to excellent.] I personally love the final two modules but that is coming through pathfinder lenses. I can imagine there being numerous nightmares in trying to wrangle it into 4E. You will be having to craft a lot of new stuff. However, with the extra resources such as cards and maps and all the other wonderful toys Paizo support the game with, I think you will have a lot of fun if you decide to go with it.
The general forum is
General Kingmaker Forum
There are numerous 4E threads including this one
4E Conversion?
And then there are some conversion notes by Berhagen that may be useful
Here
I think things are going to get more difficult in terms of conversion later on in the path and so there is going to be an awful lot of work converting things correctly.
Of note is extra resources produced by Open Design (Wolfgang Baur): Tales of the Old Margreve. These are excellent vignette additions that can be dropped into the campaign and because of their less combat focused nature, would be excellent to convert to 4E.
Best of luck with whatever you decide to do.
Best Regards
Herremann the Wise