You can do that, but it would be better to pull the i0coin-0.11.9 tag. In the future, there will be a 0.12 release with corresponding tag as well, at which point you can update (but probably won't have to).
And thus does git suddenly become a complicated mess.
The way I tell whether I need to update is simple cycle through all the coin sourcegode directories doing a git pull in each one; those where the pull got somehing are the ones that need to be re-built and re-distributed to all the machines running them. As one certainly cannot count on seeing any announcements on bitcointalk, everythign scrolls out of sight way to fast to have a reasonable chance of catching sight of something while it happens momentarily to be on the first page of posts.
How the heck would one even go about pulling from a specific tag? For all I know ome of the coin sourcecode dirs already might do that, unfortunately; I don't think git indicates that, at least not very out in your face obviously, so maybe some things already are only being updated when the specific tag that I pulled is updated, and might have entirely new tags in place by now that the old tag I am pulling is not telling me to to pull instead.
Thus usually it is much better if a given repository simple always has whatever it wants passers-by to download be right there as the default thing that anyone not trying to study up on how tags work and re-learn all over again whatever stuff they had to learn way back when they last were forced to resort to tags wil just simply get so that is all just works...
I have pulled tags before, gosh knows how though, I inevitably forget all that complexity that should in any event be avoided.
-MarkM-