I gotta admit, I really like it (e90 content)

When my son said that he wanted a 2007 335i I was very dubious. The N54 with twin turbos seemed plenty quick, but they do not have a good reputation for reliability. It was a clean example with a good Carfax and it was his money so.... It won't be as stone cold reliable as his Sonata was, but you learn something from every experience. 

Well a month or two in the radiator cracks. We've had a succession of sick animals and the vet bills have burned up our wallets, so let's fix this one ourselves. Fortunately there's how to videos for practically everything. 

OK, I'll stop blathering. It wasn't that hard to work on and frankly it's really a fun car. I see why people like these things. It's sexy, fast, good ergonomics, nice exhaust note. As a pure performance car it's heavy - particularly on the nose, but for a car that's only going to be driven to 8/10 that's not a big issue. My son's also got a hankering for an Elantra N, so maybe I'll let him get one and just abscond with the Bimmer

Caution of the possible loud Elantra N in California

I'd replace the entire cooling system, not just the radiator.  So thermostat with housing, hoses, radiator, fan, all of it.  It's all plastic and if the radiator went then the rest of it isn't too far behind.  Cooling system stuff is a 60-80k mile replacement interval on any BMW from 1992 on

Absolutely brilliant cars the tails of their unreliability are overblown. 

You'll know when the E water pump is going to fail, the car will tell you well in advance. Once you understand how to do it they're not particularly difficult to work on however some special tools and electronics are required. 

I'm the biggest late model turbo BMW fan around here and I wouldn't call the exhaust note good but I'm glad you enjoy 

I had one. Don't really miss it that much. The weight and lack of LSD kinda ruin it for me. They're fine cars, but a little expensive to upkeep, and just not what I needed by the time I got rid of it.