Submit your query here: http://www.livejournal.com/contact/?dept=billing
Other players from various games have suggested you mention you are unsatisfied with the new changes, the issues loading it, and if you're someone who got migraines from the site (I know I have three people so far who have told me they literally cannot look at the LJ stuff anymore). Regardless, please be polite in your request and you will most certainly get it. There has been word they also give back gifted accounts as well (I assume this must be asked from the gifted).
They will only refund if you bought accounts in December, but it's extremely useful for those who just bought accounts before the move.