Drawbacks? While he projects like gangbusters with a Hollywood-style camera, his live appearances, without the dramatic cheats of a staged reading, have been underwhelming.
We'll see. On one hand Teh Fred no longer is expected to sweep the nomination just by declaring; a lot of those early hopes for a unifying conservative champion have been dashed, or at least dampened. On the other hand those expectations seem to have been unrealistic, and Thompson might benefit from expectations lowered to a more reasonable level.
PS: That preference cascade article by Instapundit is a must-read. The idea seems simple, but it's a powerful explanation for swift moves in public opinion.
Basic theory? Swift moves in public opinion aren't really about the public changing their opinion, but about the public suddenly feeling comfortable expressing their long-held opinions, which had previously been falsified. I.e., the public was always anti-illegal-immigration, but only with the looming threat of a massive amnesty without any appreciable increase in border security did they feel prompted to stop offering the nice, polite, politically correct opinion -- their falsified opinion -- and offer their real one.
That article is about the sudden wash of patriotism after 9/11, but it seems to apply to many situations.