Whether it is a "weed" or not depends on you. If you consider it a "weed" it is, but if you like it and it is about where you don't mind it being it isn't.
Rugosa Roses here are "weeds because they self seed from the neighbors so readly and I have to keep cutting them out of places I don't want them. Others I know consider the coneflowers "weeds" because they also readily self seed and where they do those people do not want them. So what a "weed" is depends on whether you like it or not.

check out this post in the perennial forum. It looks alot like this

http://forums2.gardenweb.com/forums/load/peren/msg0411413218675.html?6

which someone id'ed as a type of veronica