I have had two GTPs and a montecarlo, (same family)
Monte was my first decent car 2004 ls with the 3.4 later swapped it for the supercharged engine, drove it, ****ed up a cam install. eventually sold it.
Bought my first GTP because I wanted something to play with and mod, ended up being my dd for a few months. Traded it for work done to my fusion (nice car **** motor)
bought my current GTP because I wanted a second car I could screw with (my DD is under warranty) and I found it for $450
GP are decent cars for what they are, they are comfortable, reasonably good mpg on the highway, and usually reliable. Also fairly easy to build power.
probably wouldn't buy another after this one. The transmissions are sluggish, engines are slow to respond under light or partial throttle (even supercharged) lots of mods are available but really everything needs to be upgraded now to stay competitive.
I drive a 170hp turbocharged jetta daily, from 60 up, the jetta runs circles around the stock GTP, full torque at 1500 rpm gives you a kick in the gut, and even driving hard I get 38-40 mpg. Ill probably go LS v8 next, or something turbo charged