i've got the 2's and I went up a half size which fits pretty much perfect. I like my running shoes loose though so i dont bother lacing them (they're like slip ons, they dont have a tounge). I could have probably went up a full size no problem though, then I would use the laces.
If i remember correctly, i think some reviews might have said they run narrow but I forget. I have narrow feet anyway so I didn't really notice.