I bought my first Jetta in 2006 back when they were giving away free electric guitars with each purchase. That was the cheapest Jetta they had and people were blown away by how nice the interior was. Fast forward to 2011 where you find me buying the 2012 Jetta TDI because I drive 2 hours each day and I want better fuel economy and an automatic. On balance this is a great car. The motor is peppy and the automatic is very smooth. I love the diesel, if you are going to get the Jetta then I recommend you get the automatic with the 2.0 TDI. My suggested improvments are long, but they are really quibbles and should not deter you from purchase.
The stereo (Fender Premium) is awesome. The motor makes this car your best friend. My car is black with tinted windows, it looks killer.
I would never have noticed these things if I hadn't had 2 other VWs (my Jetta and my Wife's rabbit). They replaced the soft touch dash with hard plastic, not a huge deal but it cheapens the interior. The doors open with exposed rubber gasket as opposed to the whole frame of the door opening. The rubber gasket covers steel, so it is not quite like the exposed glass that many convertibles have, but it smacks of cheapness. The driver side visor extends (most people don't know you just have to tug on it) but the passenger side does not. Why go cheap here?