I just want to say that I've been using DD-WRT for awhile on my WZR-HP-G300NH with no problems whatsoever.
I didn't notice any problems with the wireless and it doesn't seem any worse than the official firmware.
It's actually very easy to update to DD-WRT, so if you can't wait a few weeks, then update to DD-WRT now, its really not any different from updating to newer firmware.