Well being that its repeat season I havent really been watching the local channels much lately, I noticed that CBS was down when the Vikings were playing the Jets, which was supposed to be in HD but it wasnt, shot kdlh an email and they said that hd was down and would be back soon, havent checked to see if its back up. As for ABC I think their upgrading some stuff nationwide because ABCHD is down for everyone until monday.
I actually have a crappy little indoor antenna and I dont remember off hand what brand it is, it doesnt really work the best as I have to move it around to get certain channels, seems like I can always get 3 out of 4 but not all of them.
As for Charter I have Directv so Im not certain there timetable for getting HD.
If it was me I would get the STB right away, CBS has 1-2 HD games each week. ABC has MNF and some college football games. Notre Dame will be in HD this year on NBC and of course the network shows you may like to watch always look better in HD. Since you already bought it and were willing to then I see no reason not to get it again.