Although price has gone up to $120, still a steel for this great phone. It supports the 3G/4G/LTE networks of T-Mobile, AT&T and China Unicom etc. Note it is a T-Mobile phone and need unlock for other carriers and it does not support CDMA like S4.
Compared to S4:
This is not a mainstream phone like the S4 and no stock ROM available yet, it is a good idea to have a full backup before any tweaking. So, the first thing I did was to odin TWRP to it and then used TWRP to do a full backup.
At such a low price, there is no point to buy a MiFi or its kind, because this phone is far more flexible, such as adding VPN or proxy. But first thing first we need to root it, because the built-in WiFi Hotspot function is deeply crippled by T-Mobile, totally useless. Even if you can use FoxFi or ToggleHotSpot widget to enable it successfully, it'll still lead you to T-Mobile's upsell page. Even VPN is no help.
If you really don't want to root, you may use USB or Bluetooth tether which work fine though.
Rooting is very easy, fortunately, with one-click. However, the kernel is replaced during the rooting process, so I went one more extra step - odin the stock kernel. This way, plus odin the stock recovery, I can still get OTA update.
Now we can install WiFi Tether Router 6.0 by Fabio Grass. The working configuration is:
Encryption Type: wpa2-psk
WiFi Channel: 1, 6 or 11
Method: 3 - HostApd
No Firmware Reload: unchecked
WiFi Mode: G or N
ApType: ad-hoc or master
HostApd Patch: unchecked
If you need VPN, now you can use it and hotspot goes through VPN. Alternatively, you may use the native hotspot through Tetherfy etc. and use this fix. Either way, all your other devices - phones, tablets and computers, do not need to run VPN.
If I want a brand new phone at the lowest cost and If I don't need CDMA, this would be my choice of phone, not just for hotspot. It is quad-core fast, screen is good, works on virtually all GSM networks.
As always, the built-in APN is another T-Mobile bad stuff, you must add a new APN: fast.t-mobile.com as explained here.
Out of box, this cheap phone allows you to select your preferred network, 2G, 3G, 4G or LTE: