I have the 5-Speed manual transmission, and standard engine, a combination that gives plenty of power for hill climbing and passing. Fuel consumption is light, I get between 36 and 37 Miles Per Gallon using it for a commute that is some highway, and some light stop and go.
Handling is excellent, (mine has the 16 inch wheels) and the car is a lot of fun to drive. You DO feel bumps in the road, as the car is small, the tires are low profile, and the suspension is pretty stiff.
Space is plentiful for such a small (and non-boxy) car. There is plenty of head and leg room up front. 3 children can fit in the back seat, though two adults would be the limit except in a pinch. There is a decent amount of cargo space in the rear with the rear seats up and the rear seats also can fold down (separately) to give loads of cargo space if needed.
The Vibe won't hold its value as well as the Toyota variant (the Matrix), so if I was buying new, I'd go the Toyota route. I bought mine (a 2004 that was delivered in 2003), used in early 2005 and paid just $11,000. It has cruise control, CD player, rear wiper and power windows. (Everything except leather and sunroof)