I have tried powerline Ethernet before in situations where running cables was not possible and wireless had trouble too. My verdict is: run like there is a zombie attack in progress. I had ton of issues with things like noise leakage into the devices, configuration problems and oddly, a light switch that caused the network to get shutoff. Not worth the effort in maintaining it. I *suppose* if it was the only option you had then it might be ok, but if you are willing to go that route then just spend the money on a good N setup with decent antennas.
It really depends on what you're doing, Powerline networking has it's uses (home automation, long distance runs old building where wireless doesn't work and running new cable isn't possible) but for most network implementations you'll get better real world speed and a lot less headaches out of wireless N
I've had much better luck with powerline than with wireless. The powerline connection is much more reliable. The wireless connection fades in and out depending on what's going on in the house (microwave, wireless phone, baby monitor, etc.) The peak speed of the network is definitely faster with WiFi, but for my money the more reliable (and slightly slower) powerline link is much preferred.