The dual ratio has worked-out well for me (38/35t chainring, 16/19t freewheel). I city-commute during the week then ride trails on weekends. I can slip in a quick ride after work without switching bikes or ride a long trail one-way then zip home by road. Sometimes I wish I had a lower gear on...
A mix of old and new:
Shimano XT parallel-push V-brakes
Pauls levers
Salsa stem
White Industries "Double/Double" dual ratio single-speed drivetrain
White Industries Eno Eccentric rear hub
Chris King front hub
Mavic XC 717 rims