Well, yeah, the G2 isn't shipping (correct me if I'm mistaken) yet so I think it's a little hard to find any reviews. 
I too am thinking of replacing my aging Canon L - in use by me since 2008 and god knows how long before that by previous owner(s) - with something newer and maybe even longer. The Tamron is an interesting candidate. It's really a pity that Photozone has never tested the (so far) current VC Tamron - but I have high hopes in Markus as he may evaluate it like he did the 17-35. I can imagine that the G2 review is inevitable at some point so having reviews of both in order to be able to compare them would be very desirable.
I too am thinking of replacing my aging Canon L - in use by me since 2008 and god knows how long before that by previous owner(s) - with something newer and maybe even longer.
The Tamron is an interesting candidate. It's really a pity that Photozone has never tested the (so far) current VC Tamron - but I have high hopes in Markus as he may evaluate it like he did the 17-35. I can imagine that the G2 review is inevitable at some point so having reviews of both in order to be able to compare them would be very desirable.