We've got two girls traveling around the world this summer. One has a pocket wifi from Xcom Global (asia) and the other has a pocket wifi from Tep Wireless (europe).
I've become a convert to the pocket wifi in the past year. I used to be a fan of swapping sim cards but these pocket wifis have gotten better recently. The cost has come down and the coverage has gone up.
I don't have a complete report from the girls yet. I will get a full download when they are back and write up something with the pros and cons of both. The one thing I know for sure from our trip to Japan is that battery life is the big issue with pocket wifis. If you get four hours, you are doing well. I always charge up two batteries so I have a backup when I'm out and about.
I am curious if there are other vendors out there that I should know about. I'm getting ready to head to europe for a week of business in four countries and I am planning to get a Tep unless there is something better out there I should know about.