I am another E90 convert. I had an '09 328xi sedan CPO. I had it for three years. The first 1.5 years was super fun. It was fun to drive around in a flashy BMW. The inline six was insanely smooth, the RWD biased AWD was fun, tight steering and handling second to none.
After the CPO warranty ran out and things started to go wrong, I cannot emphasize what a MOTHEREFFING NIGHTMARE that car became. I probably spent upwards of $7k on repairs in less than two years, including some wild things like rear differential, AC compressor, etc etc. In fact, the straw that broke the camel's back was taking it in for a battery replacement ($600, only replaceable at the dealer.) Meanwhile I'm a full-time graduate student working full-time. Not only could I not afford it, I simply didn't have the time to deal with it. In fact, I left the dealer, drove a couple blocks over to the Mazda dealer nearby and bought my '15 6 Touring MT the same night.
If you are thinking about buying a used BMW, I urge you to think twice. Yes, there are few other vehicles that are so thrilling to drive, but considering the cost of repairs and maintenance, it is plain and simply NOT WORTH IT. LEASE one, then you don't have to worry about anything.
Back to the Mazda, I've now put almost 9k on my 6. I like the car a lot. It's truly stunning, and gets a lot of compliments. Fuel economy is wonderful. Handling is okay. Really it's hard to compare, coming from a 3-series. But, it's far better than the other comparable cars I drove. Technology isn't as impressive either. But this is a much simpler vehicle, and in the end, I'm sure it will save me a lot of time and headaches.
I love that the 6 was available with an MT. That was HUGE for me. I love the styling. I constantly look at the car and think "damn." In fact, I think this car is better looking than my E90 was, and better than the current F30. It's funny how one can be so blinded by having the roundel in their face.
My only complaint about the 6 is the road noise. I've posted about it elsewhere, but I have a whistling coming from the drivers door at highway speeds. It drives me nuts, and no solution has been found yet.
+1 for this. I really struggled between choosing a CPO E92 328 and a new 6. I ended up with a new 6 because of reviews like this one and two of my friends have E90s with pretty low mileage and have spent thousands fixing them after their CPOs ran out.
Now with regards to a 320i, I was never even interested in this car. You're looking at a completely different driving dynamic between an E90 and F30 (I think F30) and I'd choose an E90, E92 over it any day. Like other people have said the 4 year 50K maintenance is a joke as you'll get nothing out of it, unless you're lucky and get brakes and rotors after a fight with the dealership. And don't think that maintenance is "free" it's included in the purchase price of the car. Also I'd like to see some more years of reliability data for BMW's turbos as the 335's and HPFPs have been quite the debacle.
For me driving 25k miles a year I need a reliable car, a new 320i can be reliable during the first few years but later on it will probably drain your pocket. And that's ok, if the buyer is prepared and willing to sacrifice it. If looking at a 320 I would buy used, there's plenty of them with 10-30k miles for a fraction of MSRP.