Given the number of high-profile firms that actually did collapse in that timeframe, there is a certain plausibility to the claim that doing nothing would in fact cause a more general collapse.
Whether or not the experts were correct in their assessment is a matter for debate -- all we have now, is that TARP was passed, no general collapse occurred, and that a certain amount actually has been paid back.
Yes. But what wasn’t paid back and won’t be is the $$billions to foreign institutions, Fannie/Freddie, GM etc.
Here is a one very good read on the subject, IMO.
http://www.futuresmag.com/Issues/2010/July-2010/Pages/Bill-Isaac-Was-TARP-necessary.aspx?page=1