There's a plethora of MiFi devices in the market now, from Huawei, Micromax, D-link etc. When I was looking for one 2-3 years back, Huawei was the only one around and hard to get as well. Got myself the Huawei E585 then and it has been working perfectly for me till now. Replaced it with Huawei E5151 recently, since it has an ethernet port as well and comes in handy when I want to convert a wired LAN to WiFi in the office or in conference rooms.
The advantage with these devices over the plug-in ones, is that you can use them on the move as well, since they have an internal battery and you don't always need to be around a power socket. Of course you can keep it plugged in & charging if using for extended periods of time.