Zero latency, slot for USB dongle, power saving mode and usability are four important factors of a wireless keyboard.

Zero latency

Zero latency is the biggest issue for wireless keyboard. Nobody is willing to use a wireless keyboard with slow response, especially for those gamers. That also may be the reason why most of the game keyboards are wired but not wireless. In fact, a wireless keyboard can hardly have zero latency, but the response rate is really the same with wired one. If you are not a gamer, then you can choose from them both. 

Slot for USB dongle

Wireless keyboard itself should contain an inner slot for USB dongle. The USB dongle may get lost because of its small size. Designing of a slot to hold the USB dongle can help prevent this from happening.

Cover for slot should also be able to hold the dongle and batteries tightly so that batteries won’t drop down.

Power saving mode

Most of the wireless keyboard use batteries as power. In this case, power saving for a wireless keyboard turns to be important. A good power saving mode can help to save the power.

Usability

Some wireless keyboard may require frequency adjusting before it can be used. This could be very annoying. A good wireless keyboard should be user friendly-it should be “plug and play”. Many users are not willing to spend time in make adjustment to the so-called radio frequency to use a wireless keyboard.