I never understood what it actually meant when someone said that you shouldn't go for indicators which repaint.
However, I read something on the blog here: http://www.makemesomemoney.co.uk/2011/07/15/careful-of-indicators-in-metatrader-which-repaint/ which explained it.

Can we generate a list of all the indicators and systems which fall under this category as they will be systems which will not work.