I like my '03 Tdi as a commuter. Wish there was a manual diesel BMW option, I keep hoping for a 120d in the US.
VW does have hit or miss reliability. I would only buy from a private seller who can relate the whole car history to you and you can see if it’s been a good one or a frequent visitor at the dealer. I would not buy a used VW at a dealer (or a gas one for that matter).
I just got bigger injectors and a Rocketchip reflash. It really wakes up the car and you can still get the same (or better) MPG when driven sensibly.
Miatas are cheap and tough to beat in the fun to drive category, if your not worried about getting teased occasionally, but I’m not sure if they can get 28mpg highway.