In addition to the fact that most multi-line operations are painfully slow, it appears that running a macro multiple times is slow to the point that it apparently just gives up and breaks.

I have a file with a list of fields that I want to turn in to properties, so I record the following macro:

qa$C { get; set; }[esc]jq

Repeatedly typing @a after that will perform the macro reliably on every line, turning each field in to a property as expected. However if I have 20 fields to change, typing 20@a will perform the macro once, then freeze any vim input, causing an error "beep" no matter what I press. If you don't press anything, it just does the macro once then returns to normal mode after a minute or so, but if you press any motion keys it will then, seemingly at random, perform portions of the macro on random lines completely destroying the source file. Undo doesn't work.

I downloaded an actual Vim editor from vim.org to make sure I wasn't just doing my macro wrong, but it worked flawlessly (and super fast).