I too noticed the wifi issues when I got my new MBP with Mavericks. I had to stop/start the wireless service frequently. I eventually narrowed it down to some incompatibility between my Cisco Surfboard cable modem / WAP and the MBP. I reconfigured it as a bridge and connected a low-end Linksys WAP I had laying around. It solved the problem. I still think this is Apple's problem, since I'd used that WAP for years with many devices and never encountered an issue.