Dan, I consider you a friend and I even bought the 90 gallon GLASS () from you, so I'm saying this politely... But go to a public aquarium thats had acrylic widows for decades and tell me if they have those problems. High quality acrylic will not do that for years and years.
I consider you a friend as well, it certainly wasn't meant to be personal. I actually don't have anything against acrylic (I own an acrylic 300 and 55) but you asked for other flaws/drawbacks to acrylic, so I gave some.
While crazing, yellowing, brittleness, and seam deterioration are symptoms that come about over long periods of time, it scratches easily from day-one. While I don't often use sandpaper to remove algae (OK, once in a while) I have scratched acrylic tank while trying to remove stubborn algae. It has been said by others (and I tend to agree) that a glass tank is superior every day except the day you have to move it.
It is true that you don't see crazing in the really thick acrylic panes at public aquariums, but you do encounter it with your average monster tank fairly often. Public aquaria aren't built with welded seams, but rather the panes are fitted to a framework of steel or aluminum, usually set in concrete. They do yellow with age - take a look at the sea-lion tank next time you are at the Washington Park Zoo (now known as the Oregon Zoo). While you are there, check out their Amazon tanks, built with GLASS viewing windows.
The glass versus acrylic argument is kind of silly - they are both great materials, each with their own advantages and disadvantages. Depending on the application and what you want from an aquarium either can be used to construct a really nice tank...
