Wireless WILL always add latency. Period. It takes a few cycles to encrypt/decrypt the packets, then translate them to ethernet encapsulation and transmit them on to your Cable Modem/DSL Modem. Those couple of steps are 100% unavoidable in wireless. In addition, wireless devices have to wait 'their turn' until the air-waves are clear of other TXing devices before talking. This means in a congested area(lots of APs), you might get lagginess from everyeone else. This is part of the 802.11 specs, and there isn't any specific device that is immune (and still operating within the specs). It's called DTIM.
Now, as far as 802.11n hardware not being better than 802.11B/G hardware, this is very false, as far as APs go. I have a $40 D-LINK DIR-615 rev C1 AP I hack on. It has a 400MhZ ARM CPU and something like 32MB ram. This is BLAZING fast for a router. Next up, it has an atheros 9280 radio in it that can have 100% of encryption and decryption offloaded to the wireless card (which has dedicated hardware for it. These newer radios do a MUCH better job of receiving signal in noisy environments. 802.11n speed is not the only benefit of these radios.
As far as people talking about using an AP as a connection device for their PS3, this works very well. Look up 'Wireless Client' mode, or 'Wireless Bridge' devices. I've done this a few times for fun (not with my ps3, though), and it does work quite well. With the correct AP (I was running a custom Linux AP solution) that supports VIF/VAP per client mode, you can't even tell that you're wireless.
In the end, wired is the best solution. Always. 100mbit wired is better than 150mbit wireless 8 days a week.