Pretty much every shot I take with the M9 is at 1600. I don’t go above it. I do wish the M9 had better high ISO quality though. There are times I’d really like to be shooting at 4 or 5.6 but I’m constantly wide open. Maybe NYC is a dark place…I don’t know.
The forums can be really misleading if you use them to judge what ISO you should stop at. Often those guys are so into the whole pixel peeping thing that they don’t understand photography. If you can find the right balance between gear/pixel peeping and actual photography, you’ll be better off.
Best of luck with your own shooting!