When I hooked Ooma’s telo unit up I followed the suggestion that, for best audio performance, one could cable it in series between the modem and router. This seemed to work fine until I noticed really slow internet upload speed. Checking with Speedtest.net showed download of 30+ Mbps, upload of 0.4 Mbps! My first thought was to call my service provider but then I tried hard-wiring my laptop straight to the modem, retested, and got 10+ Mbps upload. Now suspicious about having Ooma in the middle, I recabled following the more basic config: modem to router to Ooma. Everything was suddenly fine with upload speed around 10 Mbps even on wifi. So the Ooma unit apparently didn’t like passing signals in the upstream direction. So far I don’t notice any difference in audio quality (which has been great in fact).
I suppose my setup could be unique, but anyone who is considering the alternative hookup method might want to do a speed test before and after.