My first PS2s are no longer functional (one was bought on the same week of the european release date). I reverted to the slim ones a few years ago and they've been great ever since. My pet peeve with the original version is that the discs always made a lot of noise while the game loaded. I recognized this but when my mother used to play her Silent Hill games she associated the sound with the "scary moments".

You could probably do well with a used slim, but you never know. The price of a new ps2 where I am has dropped drastically in the past year.