My experience and review of the Panda 300Mbps Wireless N USB Adapter. It did provide greater signal strength and compared to your standard wireless card, this did provide further coverage.
It did however struggle load webpages even when sitting outside my front door with the wireless router in my basement. My router is: ASUS RT-N66U Dual-Band Wireless-N900 Gigabit Router so even with a good router like that, it didn’t work as well as I wanted.
I’m still very satisfied in this usb wifi adapter and would recommend this especially for only $20.