I own a few G&Ps. Older generation tend to have hop up problem, which means they do not work too well. But the new ones e.g. Stoner machine gun, have solved this problem, and have great rate of fire right out of the box.
If you have $400 budget and look for a airsoft AEG which can perform well right out of the box with reasonable reliability, King Arms, G&G, G&P, VFC are all good choices.