Reindent lines just doesn't seem to work with C++, here's a fairly simple case
printf("Hello, world.\n"); // I am simple
(I think the site strips whitespace so just put in some random leading whitespace, which is what reindent is supposed to fix.)
Try to reindent it. Doesn't work right.
It seems like this is a simple enough example to pretty much say the feature doesn't work. Personally I can't use it, this is my #1 issue with sublime text, I've switched from emacs and I miss the feeling I had with emacs indentation that whitespace was basically all taken care of for me.