Any control issues Japanese gamers might have with Monster Hunter 3G will definitely be improved by the Circle Pad add-on that will be releasing alongside the game.
However, Americans (and everyone else) will have to wait just a little bit longer. Although Monster Hunter 3G currently isn't scheduled for a U.S. release, Nintendo World Report notes that the Circle Pad is indeed heading to the West. Capcom's Ryan McDougall said as much during the New York Comic-Con this year, noting that the Circle Pad would be available around the same time that Resident Evil: Revelations launched.
Resident Evil: Revelations is slated for February 7th in the States, but we wonder if the Circle Pad (or Circle Pad Pro?) will be available earlier, or in a bundle with the game. Either way, it might not matter for importers. It's not like the Circle Pad is region-locked or anything (at least, we wouldn't think so).