I have read that some users have had issues Porting their R.W. out to another carrier. Some do have restrictions and do not allow VOIP numbers to be ported. However, I see many other posts of users that successfully port out just fine, even to the same carrier that another person reported issues with…so that is a gamble i guess.
As far as pros/cons… I do think its overcomplicated and unnecessary as the tech is pretty much built into the device and backbone carrier already. However, in this case, there has to be some intermediary gateway interface that makes it a MVNO. That interface is the R.W. app. Without that, and u can get that by becoming a customer of that carrier backbone (tmobile).
The idea off a user level (non system) app having primary control over the devices communication ability is certainly a less reliable idea than full native carrier. Apps can crash, or run into compatibility issues. Especially if use a Pixel device where you are among the very first users to get OS updates. So thus, those users will be the first ones to have issues. Also, those advanced users who run custom roms and mods.
With Android continuing to evolve, a user level software solution to make all this work is risky for the future. Android P already is kill the ability for idle apps to use any of the devices sensors and other more things in the name of security. There may come a time where R.W.s patented approach to this Hybrid calling is no longer possible. That is kinda why I am curious as to how R.W’s implementations compare to that of Google’s own Project Fi’s similar implementations.
In my brief testing, R.W.'s tech seems to work quite well, on my current test device and area. My mothers Moto G 1, on the 2.0 plan (Sprint) the call quality isnt that great, but I am more certain its the device itself that to blame, as that is not the case when I tested using a Nexus 5X and the tmobile based plan.
One thing i didn’t get tested, is what happens when the phones connects to a open wifi that requires you to “log in” by opening a web browser and accepting terms etc. Or for a corporate network that requires special secondary validation or is in fact a Intranet with no outside Internet(WAN). I would assume the R.W. app is smart enough to detect that the wifi connection has no Internet access, despite a strong signal, and will thus use Cell. Same question I have for Fi. I have read that Fi app is much more aggressive with auto connecting to “free” hotspots all over the country. Where as R.W, for the 3.0/4.0 plans BYOD, it goes based on the users manual wifi selection. (the older 1.0/2.0 phones did indeed force wifi on and was more keen to force user to use wifi).