Wireless Network Data Transfer Rate - What to expect?

This is quite a simple one I guess to those who know so if you can help I would be grateful.

I have just upgraded my wireless  to Wireless N 802.11n and Windows Network Centre tells me that I have 270Mbs on both the Dell computers I run. However when I tranfer files from one to the other I only get a transfer rate of 1.8Mbs. I think i may have misunderstood but I do not know what exactly.

Also my signal quality is only 3/4 bars out of 5 on the windows signal quality indicator with a distance of only 8m through the door and turn left or 6m directly through the wall The router claims 50m range in a building.

Am I being shortchanged on both of these or this this to be expected?

Thanks