is a 256 x 2048 map still a good power two map?

I often tile my UVs at least into one direction. So i mostly come up with long maps like eg. 256 x 2048px. I wonder if these are still good power of two maps for an average 'standard' video card?

Yes, that’s fine. You will have a hard time finding any cards that do less than 2048 pixels; any that do exist will be very old by now. (Aside from iPhones and iPod touches made previous to the third generation, which are limited to 1024.)