I just moved into a new house and haven't yet started Internet service because I have lots of construction going on and am not sure where the cable modem will eventually go (part of the construction is networking the house, and I haven't decided where the network cabinet will go). So in the meantime I'm using the hotspot feature on my Nexus 5 for LTE internet. I get about 5-10 Mbps down, 3-5 Mbps up at this location (500 feet further uphill at the sandwich shop it's 30/9 Mbps, sigh).
My service is with Sprint which typically has spotty LTE service, but fortunately my new home is well covered. Sprint also teamed up with Google so my Sprint number is also my Google Voice number. This means I can make Google Voice calls over LTE via the Hangouts app (Google moved Voice to Hangouts a couple months ago). The app still needs a lot of work (e.g. doesn't integrate with the contacts directory yet) but call quality has been stellar - nearly indistinguishable from when I'm on wifi. I'm actually surprised how well it works considering it's going over a cellular data connection. I mention all this because Sprint is the network most MVNOs use by a huge margin. Since their LTE network is certainly capable of VoIP, any problems you encounter with it are likely to be due to the MVNO blocking VoIP.
Latency has been pretty good too. Speedtest.net reports my ping times between 40-45 ms. I occasionally play GW2 over this connection, and generally I haven't noticed any more lag than on a wired connection. Occasionally there's a hiccup like you'll sometimes get over wifi, but its infrequent enough that it hasn't degraded the gaming experience. Overall it's been pretty indistinguishable from FIOS (what I had before the move), and better than the cable internet (I had Time Warner before FIOS, with 150-250 ms ping times).
I'm on an unlimited data plan, so conceivably I could go on doing this forever. The main issue I'm running into (one you shouldn't encounter with a dedicated hotspot) is that my LTE disconnects when there's an incoming call. There's some obscure reason I don't recall at the moment for Sprint and Verizon's phones not being able to do voice calls and LTE simultaneously, even though they could do it in theory. Voice calls go over the CDMA radio while LTE goes over the LTE radio. Unfortunately since my phone is designed to be, well, a phone, I haven't figured out a way to disable CDMA so I can receive the incoming calls over Google Voice. The regular phone dialier and Hangouts both ring when I get an incoming call, but the regular phone dialer locks out the phone preventing me from switching to answer the call via Hangouts (I'm not even sure that would work since it seems to disconnect LTE the moment the phone rings).
If you plan to do this with a hotspot, make sure you can cancel the contract if there's poor service at your house. A tenant at the building I manage opted for LTE Internet (because Verizon DSL there sucks). The building is within their LTE coverage area, and I get a good LTE signal from the roof. But at ground level his hotspot defaults back to 3G and he gets terrible Internet speeds. Unfortunately he got excited and ordered this a month before he moved in, so was outside the cancellation period by the time he moved in and discovered this problem. But I would check first to see if you can use your phone as a hotspot and just beef up the data on your plan.