I've been using NTC's dongle (USB) for the past 10 days or so and the internet speed is quite acceptable and considerably reasonably priced. Sure, there are times when the speed is moving at the pace of traffic in Thapathali at 5:30 pm, but more often than not, I've barely had any issues. 

From what I hear, NTC's speed is faster than Ncell's. If you really need blazing fast internet, WiMax is the way to go but again, it all depends on what your needs are. For unlimited internet, you always have the option of subscribing to cable internet. 

To subscribe, you need go to NTC offices in Pulchowk or Dharahara w/ two copies of PP pics and a copy of your citizenship. You'll be paying Rs. 2,200 and that's inclusive of a dongle (1 GB USB) and 3 GB of data Package. Renewal is seamlessly easy.