George,
Oh, where to start.....
I'll just go through a list of his best known efforts and give my perception.
Dornick Hills - 16 of 18 holes still routed pretty much the same, 1 and 2 changed beyond repair. That is about it. Perhaps one of the best candidates for a total restoration.
Twin Hills - Routing in tact, most of the holes play the same. Greens have been touched a few times and are much more tame than originals. The 8th hole is perhaps the one glaring change.
Muskogee - Changes on four holes in the routing and a green redo by Tripp Davis. Otherwise, fairly consistent with original course.
Hillcrest - Redone in the 60s to make way for new clubhouse and changed four or five holes because of it. Several aspects remain intact, but the bunkering and a few greens have obviously been changed.
Melrose - Only a couple of holes retain anything of the original course. Unfortunately, this one is lost forever.
Oklahoma City - 17 of the holes are pretty much in tact, only the 15th and new tee on 16. Greens have been touched but still have Maxwell feel to them. Don't believe any of the reports that Tillinghast touched the place. Club records indicate differently. Bunkers have been changed over the years to be more in line with the modern look of Southern Hills.
Crystal Downs - Excellent course that is pretty close to original design. Not much more I can say that hasn't already been said.
Southern Hills - A lot of subtle changes have been done over the years. Only one hole has been significantly changed, the 7th. The bunkers are nothing like what he did. The greens are similar but have lost something due to a lot of tinkering. Keith Foster did a fine job of trying to recapture a lot of Maxwell's work, but it is just not the same.
Prairie Dunes - The original 9 holes have a very similar feel with the exception of added length. The 7th and 17th have had some additional work done to them. But otherwise those holes are very similar to the original design.
Old Town - Some minor changes over time. Greens have been redone though. They still have a Maxwell feel to them, but from all reports, just not quite as good as the originals.
Colonial - Touched so many times, there is nothing of Bredemus or Maxwell left on the place except for some of the main hole routings.
Oakwood - One of the best courses out there with most of the original course in tact.
Lake Hefner - Totally redone. Ironically, most of the current course runs in reverse over the original routing.
Oak Cliff - Has been retouched a couple times at least but from what I have seen has most of the routing in tact and most of the holes have the orignal intent still in them.
Hope that helps. If you want more concrete info, PM or e-mail me.
Chris