I noticed there was no thread for the 50mm f/1.0 lens so I thought I'd remedy that.
Sure, for most people this lens is irrelevant. It is no longer in production and used copies are quite expensive ($4000-$4500). It is heavy and very slow to focus (slower than the f/1.2 lens), and quite frankly, it is not as sharp as the f/1.4 lens.
This lens can be used at f/1.0 - something no other EF lens can match - in fact, it only makes sense to use this lens at f/1.0 because otherwise the f/1.4 lens will significantly outperform it.