I have done it. 2 lbs was a little much and I could definitely taste it. It got better with time but was not great at first, of course that could have been my batch.
It's like honey in the sense that people think adding honey will make the beer taste a bit sweeter or have honey-like flavors. It doesn't. Half of the impact is the thinning out of the malt flavor just like when you add corn sugar. The other half of the impact is the flavor/aroma. Depending on how you do it, keeping aroma factors from honey or agave is difficult to impossible (just my experience) so you are down to a thinner taste and a residual flavor impact. And the agave I did wasn't super. It was OK. So good luck, maybe yours will be much better and I hope delicious.