I have a VMG8324 but I personally find it works very well on my line, so Im talking from the perspective of the VMG8324. The VMG1312 is only 10/100, which rules out one of my important personal requirements and spec wise its a little brother to the VMG8324, but DSL performance based on its chip should be the same.
Some versions of the f/w have been a bit wonky but I stick to an older version which I find stable.
It gives me circa 3.5Mbps more headline sync than the HG612 which in turn also gives 3.5Mbps more than the lantiq chips despite being on an ECI cab. I posted some stat comparisons in the review on the main site. There's also some stats knocking around from about Oct last year when I had a line fault as I put the HG612 for a short while, but switched back to the Zyxel as it was producing less Err/Secs than the HG612.
However I cant stress enough that performance of routers varies from line to line. les-70 had a vmg8323 which gave him more Err/Secs than the HG612 although it did sync at a higher rate. Generally speaking on most lines it does seem to eke out a bit more speed, the major complaint about it seems to be silly f/w bugs in some versions.
Is it fully G.INP-ready?
VMG8324 is full G.inp and G.Vector ready.
Theres a couple of the regs on here who use a VMG8324 and who had no g.inp issues with it working straight away with g.inp Mk1.