Firstly, for the record, that article reads like it was written by an idiot....
BMW sixes are the best in the business - they sound awesome and rev very well up to redline. Very expensive to get that six in Aus though as the article says.
It depends on what you're after...diesels don't sound the same and you can't really cane them over a nice big rev range.. Can't argue on torque and fuel economy though! Lets face it though, fuel economy isn't REALLY at the forefront of a BMW purchaser's mind!!!
The 323 is a dull drive however, so the diesel is probably more fun if you use the torque. At this point, I have to say the thing that makes the biggest difference to the drive is whether you select the auto or manual...
SO, I'd say the only downside to the diesel is the sound and smaller rev range.