No ! ...don't just take my word for it ! ...go to the shop which has both the D300 and A55 and try them out for yourself. Small body and EVF may not be everybody's cup of tea.
...for me, what's important is the end results, if it allows me to shoot better and faster, increase the ratio of 'usable' photos taken, then that's the camera for me.
errmm, sorry for the late reply.
Shoot everything ! ...if it moves, shoot it ! if it doesn't moves, shoot it as well !