I haven't tried all VOIP software but of what I have used, inbound is always a bit of a problem. If someone has a high dependency on answering inbound calls when they are made, this solution may not be right for you.
In my own case, I don't have that dependency. I usually just let calls go to voice mail which is then immediately forwarded to me as an email. When I see it's actually someone I know (not telemarketers, pollsters, etc), I can VOIP outbound call them right back immediately (or at my convenience). I've found Skype with the $30/yr subscription to be able to call any land line of mobile number yields an excellent outbound call quality through non-phone devices. People sometimes comment how clear the call is and are surprised that I'm calling through my laptop (or soon this Mini)... usually via someone's free wifi.
So generally, if inbound answering of live calls is very important to you, I'd think twice about a non-cell phone solution. If your calls are few and/or voice mail + call back can work for you, replacing a cell phone with a Mini LTE can save you $1000+/yr. I've got by just fine for many years using a laptop + ($30/yr) Skype (and a cheap MiFi plan in "need to call now" emergencies). For my situation (which is relatively limited in terms of on-the-go communications needs), $30/yr is a HUGE win vs. $1200+ per year going to AT&T, Verizon or others.
I look forward to the more portable Mini becoming the main device for this application for me. Mini + Skype app + free wifi should cover about 90% of my own calling needs. Occasional activation of LTE/3G when I really need some internet or I really need to make a call and can't find some free wifi will cover the other 10% of the time. No more carrying the MiFi and it's charger. And sometimes, I won't need to lug along the laptop and it's accessories either.