People who are about as "inside" as you can get - Andreas/Roger say they are very solvent.
Roger Ver spoke in a youtube video a few months ago. But he did not see how much is left in the wallet: he sees MtGox have big numbers on their bank account, and he has no way to know if the digits add up to the total incoming transactions - too easy to cook and hard to verify. Even if he is sure the fiat is there, he didn't mention the coins are there. Besides, he said MtGox doesn't have liquidity problems to offer fiat withdraw, that is a bit different than solvent.
http://www.youtube.com/watch?v=4pSYJiXQgbMAndreas Antonopolos didn't say anything related to MtGox's solvency recently. He did mention the opposite in another youtube video, that the transaction on MtGox happens on the book, not in blockchain (implies that he doesn't know), and he mentioned in a fraction-reserve system transaction also happens only on the book - a bad way to express it, hinting MtGox is reserving only a fraction of funds which he didn't mean.
http://www.youtube.com/watch?v=JP9-lAYngi4So I cannot take these information as Andreas/Roger claiming MtGox being solvent. Did I miss something? Kindly add more information:)