I talked to a guy who completed the hike a day ago. Here is what he said about switchbacks:
Don't worry about all the rumors you hear about it, it really wasn't that bad. The first half mile from guitar lake is a bit difficult to find the switchbacks because they're covered in snow, but it was fine with microspikes. The switchbacks at the top were easy to use as well, it's snow covered until about half a mile from the summit, but again it was fine with microspikes. People had carved out footholds on any part that needed them. With microspikes and an ice ax, it's entirely manageable. Same with forester pass.
Edit: the above paragraph is addressing the west side of Mt. Whitney -- the John Muir Trail where it climbs Mt Whitney. Forester Pass is about 15 miles north of Mt Whitney on the JMT.
