Yes, google "Mifi disconnect" and you'll find endless stories of Mifi problems with the wifi mode (it works perfectly in dongle mode), across carriers: Verizon, Spring, Virgin Mobile.

Bottom line (sad to say, since I own two): the Mifi doesn't work in wifi mode reliably. It drops offline every few minutes, breaking your ssh connections and any downloads in progress. It does reconnect within 5-10 seconds, so it sorta looks like it's working to your average undemanding browser user.