It's been awhile since I did a search for shower doors. My tub is 6' rather than the more common 60", and I was trying to stay off-the-shelf, and not go custom to save some money. There were few choices, and Kohler was one of them. With a 60" tub, you'll have lots more choices.
The reasons I'm not thrilled with the Kohler door: it's white, powder-coated finish and chunks have popped off in various places, the handles/towel bars are really flimsy, the track design (it's a semi-framless, i.e., a frame on the top and bottom) has lots of friction, the holes in the glass to attach things were not clean - there were chips all around the edges - chips are where cracks start (think they bought the glass from China!), the bearings out of the box were not great and the thing never slid nice and smooth or quietly from new, the bracket to hang the door had several holes, and the lowest one was still too high. Consider that you don't cut the verticals, they should know how high the thing should be! Their design for sealing the ends is poor. It was not a pleasant purchase when you add into the fact that they promised delivery from the factory in two weeks, and it took over four months (not that big a problem, as my self-remodeling project dragged on). But, to have the distributor call, be promised it would be shipped today, then find out it wasn't over and over again...I lost faith in them. IMHO, Kohler has some nice designs, but they also have some dogs - they are a NIH kind of company, and kind of snobby. They seem to want to do things their way, when everyone else does it different, just to be different, not necessarily better.
We have some great engineers in this country, but corporate attitude and direction for them is critical to producing great product...I think they've lost focus. For that reason, when I do shop for something, I avoid them. Your results may differ. This is one person's opinion...
With most designs, when the corners of the enclosure are not square, you will have to do some custom fitting.