Today is the 5 year anniversary! Feb 28, 2007 through Feb 28, 2012. I thought I'd post my stats:

795 round trips of Folding Bike + Amtrak commute (Center City Philadelphia to Malvern, PA)

6,758 MILES BIKED (8.5 miles / round trip)
270,300 Calories Burned (That’s 77 Pounds of Fat)
47.4 Vertical Miles climbed up Cedar Hollow Road (Paoli, PA) (315 ft hill in 1/2 mile)

42,135 Miles NOT driven
1,685 Gallons of Gas NOT burned (@25mpg)

Total Bike Expenses $1462
Bike cost per trip $1.84
Bike cost per mile $0.22

Approx. $4200 saved overall vs. driving (including bike costs, train tickets, car insurance savings, extra food costs, car driving avoiding savings etc.)

Bike #1: Downtube NS total overall expenses $696, lasted 422 round trips (3587 miles / 3 years) then the seatpost cracked.
Bike #2: Downtube 8H total expenses to date $766, 373 round trips (3170 miles / 2 years) and going strong.