I like plexiglass for some purposes, but after a while, you can see the effects of cleaning. When you can clean without physical contact or without using chemicals, it is good. It is more "transparent" than glass for framing, and for book shelf covers, if you can use it frameless and clean it in a shower, rinsing with hot water and not wiping, it works well. (That also works well for sunglasses.)
We also thought about a partial wall in our shower with glass above. By the time I looked at the way the glass would be framed and the cost of custom-cut glass to adjoin the shower door, along with the use of caulk at the base, it wasn't as appealing. When you can build a shower without using caulk inside, you don't have that strip of what eventually looks dirty and must be cleaned frequently until it is eventually re-caulked. I like low-maintenance when we can get it. We chose tile with epoxy grout, and a high-mounted shower. Let's see how this works out in the long run.
We use only one 100 cfm fan, centered near the shower. That works well enough for all purposes. But Mitchell makes an excellent point: bath exhaust fans are for moisture as much as anything else. There are a number of moisture-absorbing or moisture-collecting surfaces in a bathroom. If you don't eliminate the moisture while it is removable as steam, you provide support for microbial growth. Bath fans are an important part of humidity control in a home. Design for humidity control should be for reducing excess humidity and maintaining a healthy level of humidity during dry times. Unlike Mitchell, we don't have trouble with use of the fan - hard to use a bath mirror after a shower if you don't. Vent fans are good for laundry rooms and other "wet" rooms also. There are some that will automatically shut off when a certain humidity level is reached.
I like using/reusing materials too. (beginning to need a larger storage space) We have leftover glass blocks that will find a purpose at some point, perhaps in a greenhouse or sunroom. Good for letting light in when you need privacy, like a bath window, or for adding at a high point in a wall instead of a window.