Last year I went for a test ride with a couple tri buddies. They can't ride in even a loose paceline (not that I can ride a tight one). Squirreling left and right (specially in aero), into traffic, no signalling, unpredictable moves, and they missed pointing a piece of wood on the road, in fact they just rode a hair's width next to it and I ended up riding almost over it - I nearly wiped out and was soooo pished off. I won't ride behind them anymore. Ever.