A new tuner known as the Rafeal R828D has become officially supported by the main software branch of RTL-SDR. Comments on the initial testing from this thread on the Reddit RTL-SDR forum show that there is no real improvement over the cheaper R820T tuner, and that a hardware mod is required to get acceptable results from the tuner.

On the Reddit thread user metropolis_pt2, the developer of the driver for this tuner writes

Internally it seems to be almost identical with the R820T, the only real difference is that it has 3 inputs instead of only one (Air-In, Cable1, Cable2), of which two are connected on the Astrometa DVB-T2 stick. Air-In is connected to an external (probably LC-)highpass which seems to have a cutoff-frequency around 320 MHz, and Cable1 to a low-pass with a similar cutoff-frequency. The driver I’ve added will switch automatically to Air-In if you tune > 345 MHz. The filters are not sharp at all though (not surprising given their low order, I only see a few capacitors and inductors in the input path), and their added benefit is a bit questionable. You might get a bit less WFM interference at, say, 900 MHz, but that’s about it…

In Antti’s LinuxTV blog, Antti talks about the internals of the device and shows many pictures of the insides.