In reply to mlmatt:
I tend to carry the two smallest sizes (pink and red) and probably use them on one route in every ten leads.
I placed a pink one last night in a small horizontal crack that was not wide enough for the friend I would have put there if it was wider.
They have their uses but it depends if you like climbing with a full rack of gear because you have it or if you want to strip it down to the minimum. I'm already carrying a >10kg beer gut up the crag so a few grams extra for some tricams is not going to change my climbing.