Rented Starmifi from Justin for 11 days, pleasant guy that explained how to use the device and also offered advice on Japan. Had some issue with the mifi when in Japan (kansai region), but luckily Justin responded and resolved the issue even though it was really early in the morning.
Coverage was excellent, battery life is enough to last for the whole day when fully charged.
Apart from the reliable connection, its also one of the cheapest deal out there. I only used 3gb of data for my trip even though me and my gf have been using google maps and trip advisor intensively throughout the trip, so this is a better plan compared to those unlimited daily plans.
Will definitely get back to him for future Japan trips, thanks Justin!