I've been using the Millenicom MiFI 20 Gig plan now for about 6 months. As others have said, no router needed. It works fine as long as you are within about 30-40 feet of it. And remember it's portable and the battery lasts a LONG time. Put it in your pocket and head off to the park with your notebook/Ipad/Nook. It will accommodate up to 5 different devices at one time. I even set my phone to search it out and use it if available.
I also got the Sleek - it seems to add about 2 bars to the MiFi. And I got the Sleek office kit to put in my 5th wheel.