IMO, Yes, overkill, unless the conditions warrant it

I've always wanted a bivy too, i thought it would be a good emergency or ultralight shelter. I ended up getting an OR gore tex bivy, similar to that one, and have never used it, and probably never will. It's really too much weight to carry around "just in case" something happens. the only reason I would want to carry it is if there was a very high probability that I'll be needing a shelter. At that point I would much rather have a small tent. They're probably really good for what they were designed for, an emergency shelter when you need to travel extremely light in adverse conditions, like summiting a mountain. But for me, I think it's too big and heavy to really be an emergency shelter in regular conditions, and too small and specialized to really be used as a regular camping shelter. So I guess it's either too much, or not enough, depending on how you look at it.

I just finished making a silnylon poncho based on the ID one that you have. I haven't had a chance to use it yet, but I think it's just much more versitile than a bivy. How do you like yours?