My flatmate got home and was complaining that his front shifting was a bit crappy.

He doesn't look after his bike much.

I changed the chain & cassette on my commuter the other day and got vicious chainsuck in the small chainring.  Professor Chainsuck (aka Jonathan Levy) tells me it's all about the teeth wearing down to a slight sharkfin shape so that they hook over the new chain at the bottom of the chainring, and won't let go of it.  Which looked about right:

This chainring is not a common size, google didn't find any available locally, and it was going to be NZD $50 to import one.  But J Levy's site also mentions flipping chainrings over the other way around so that the shark-fins are pointing in the other direction.  You can then use them for twice as long, perfect for a cheap bastard like me.  Unfortunately, after flipping my granny I still had chainsuck, but it turned out it wasn't caused by the shark-fins any more, it was caused by the splayed-out widened bits on the worn side of the teeth getting wedged in between the inner side plates of the chain.  I filed those bits down, and then it worked like a dream.

Apparently middle and outer chainrings are not flippable because after flipping the ramps and pins would be facing the wrong side, so that you can't shift up to them.