2009 seems to be a good year.
I've talked about it here before, we've got an '09 TDI DSG Jetta. Mostly trouble free and one CEL in 70K miles.
Oil changes are more of a chore, have to use ramps, no good lift point in the front for the floor jack thanks to the under engine/trans splash shield, and there are eleventy billion torx screws to remove. However, it only needs serviced every 10K miles, and with the cordless Dewalt the screws come out quick. The VW spec synthetic is pricy too, especially if you're used to parts store brand dino juice.
The CEL was for a failed cylinder pressure sensor, which is integral to the glow plugs. With some help on this forum and a Bentley Manual it was a 15 min repair, taking my time. Though those glow plugs are spendy at a buck fifty each.
DSG requires 40K mile service interval, can be DIYed if you're willing, but to do it right requires VAG-Com and some special tools. Paid the dealer a little over $300 and provided the fluid, filter, and seals myself.
Everything else; oil, oil filter, fuel filter, air filter, cabin filter, etc. have been easy DIY stuff.
The only other fly in the ointment is a very recent issue with the key not going into the ignition. Apparently the spring loaded dust cover gets worn and hangs up preventing the key to go in. I borrowed a bobby pin from SWMBO's hair to wiggle it back into place so we could get home. It did the same thing this evening. I found some threads about it on TDIClub and VWVortex with suggestions, so I lubricated it with some Liquid Wrench, and proceeded to insert key, turn ignition, and remove key about 50 consecutive times. Maybe it's "fixed" now?
There's evidence of possibly higher than should be acceptable failure rate of the high pressure fuel pump on the common rail diesels. There's a long thread about it on TDIClub, but the NTHSA didn't find it warranted a recall after their investigation. I know there have been legitimate failures, but believe there has been a lot of internet hype touting the issue as being more prevalent than it really is. Never the less, we use Stanadyne Diesel Performance Formula additive in the fuel about 90% of the time to aid in lubricating the fuel pump, since the modern "dry" low sulfur diesel is claimed to be the primary culprit for the failures.
All of my experience has been on the A5, but I believe the New Beetle is an A4 and the "new" New Beetle is an A5.
Cliff Notes, we like our A5 TDI Jetta, limited issues, acceptable enough maintenance for the smiles/miles per gallon.
I don't know a lot about the New Beetle, we serviced some at my old job, I remember plastic oil filler necks breaking, fluid leaks, and every one of their interiors smelled like a box of crayons.