I ride 14 x 2 commuting on a fixed gear Giant Bowery. I have ridden it 30 miles on weekend rides. I've also ridden my stock Pista on the commute, and also 20 milers for fun.

No pain issues for me, other than some slight wrist fatigue occasionally on the Pista. Not enough positions on the Deda Pista bars for long distance comfort. Not major, tho, and certainly doesn't stop me from enjoying the bike.

I'm with the above thoughts: if you're a regular rider and can't go 8 miles without pain, you need a fit. Pronto.