I'm a huge fan of Pontiac Grand Prix GTP's and Buick Regal GS's.
But both of those cars have the Series II 3800 engine, it runs forever without skipping a beat. I think that the Regals are more comfortable inside than the GTPs are, but that's just me. Other than the interior seat comfort, it's basically the same car. Oh, and they do both have transmission issues, but as long as you aren't routinely dropping them from N-->D or switching between R & D while the car's still moving, it'll last you quite a while. I know several people with between 130,000 and 150,000 on their Regals and they haven't needed to buy a new tranny yet... the car's still running fine.
I'm actually looking to buy a 99 Regal GSE that has every option and very low mileage for right around $10,000 sometime next week... if I can get the financing for it :'(