The range extender I bought is very simple to use and does a good job at what it is designed for: You plug it in, and with a few configuration steps, you're in business extending your WIFI signal. But range extenders do have significant limitations.
First, most range extenders have a single radio per band. And therefore any traffic carried by them is going to be at about half speed. Why? Because a typical range extender is a pass-through device: every byte received by the extender needs to be immediately rebroadcast over the same radio channel. That means a range extender needs to handle double the radio traffic of a typical router, effectively halving its useful throughput.
client ⇄ extender ⇄ primary wifi
Secondly, most range extenders are only range extenders. They are not programmable routers. You can not use them to build a "guest zone" or any other kind of new network. They generally do not operate as a gateway, but as a bridge. There is no way to manage IP ports or implement a distinct WPA2 passcode. And that greatly limits their flexibility.
In short, I'm glad I bought this extender - it is a fun toy and may be useful in a hotel or other zone where one can't improve the location or operation of the primary wifi access point. But for home use, where the primary wifi base station can be re-located, re-configured, or upgraded, a range extender has limited utility.