We live in a brand new semi-detached house. Have these devices now 1 year in the operation - 4 pieces. I often play at night online; ie no other device in the house running - even all lights off. But every 15 minutes I get a disconnect and then felt that lasts 1 minute to everything caught again. My Händy connected in time via WLAN and proves that the Internet connection works in general - only the Powerline goes now and then offline :-(
Conclusion: Would not buy today, and instead put a repeater in the 1st floor.