Actually, the A2DP implementation on the Tesla is pretty good. Some A2DP stacks only support the low end SBC codec, but I think Tesla's supports something better since it sounds better (MPEG-1, MPEG-2, MPEG-4, AAC, and ATRAC are all options to the A2DP spec). Obviously, it depends on the A2DP support in your connecting Bluetooth device to get better than SBC. I've used an early generation Bluetooth receiver in my Mercedes to get A2DP and it sounds much worse (probably SBC, intended for audio calls). Is it awesome? No, but certainly we're not talking about streaming high fidelity lossless anyways from websites. The A2DP quality is pretty much indistinguishable with say, pop music from the USB drive with the same AAC encoding.
My only issue I find with it is the lag - it is hard to use the Tesla's sound system as surround sound speakers for an iPad playing a movie because the audio sync is not good, it's about 0.25 or 0.5 seconds behind.