Lots of posts on here but Ill try and sum it up for you as a 159 2.2 JTS owner. In general they are a great car, I have had no real issue with reliability and you can see the looks of exterior/interior for yourself.
Main issues that are considered general to the 2.2 or 159 are as follows:
1) Hesitation at low speeds - Get a Mango Mod 4.(Even if your car doesn't have any hesitation get the mod anyway - its great
2) The squeeking windscreen issue - most owners have had this fixed but it can resurface - dab of silicone spray round the window rubber usually sorts it for a few months.
3) Fuel econmoy is lower than advertised. Different people claim different rates but its a big heavy car so i think you will do well to get 25mpg normally or 30 on a long run.
4) Tyre wear, big 19" and expensive tyres. Get your tracking checked and get is set to zero toe out.
Other than that there have been many and varied issues. One or two people on here have horror stories about the 159 but I think in general it has been well received and most owners are happy. Getting yourself a good dealer or independant is key IMHO and can really sooth the bumps.
In short Im well happy with mine and seriously considering chopping it in soon for the Ti or cloverleaf version so it cant have been that bad.