I still doubt the whole conspiracy was as much a threat as it was made out to be, IMO the threat was blown way out of proportion by Cicero. firstly because he loathed Catiline, and secondly, the whole affair would make Cicero's term as consul one of the most memorable in history and help to cement his name in the history books a "The man who saved Rome".
The fact that Catiline was a bad apple and a want to be 'demagogue' is pretty clear but the accusations of overthrowing and murdering the senate were far fetched to say the least. Catiline was everything that Cicero hated, for a start he had been Cicero's opponent in the run for the consulship, he lived a playboy lifestyle, was handsome, good with the ladies, wealthy, with impeccable Patrician ancestry, he had everything handed to him on a plate where as Cicero had to work extremely hard against all the odds to get where he was. Cicero needed a target to make his consulship one to remember and Catiline fit the bill perfectly.
I'm not saying that Catiline was an angel or anything because he wasn't, he was a nasty peace of work, his actions during Sulla's proscriptions prove that, but what I do think is that Cicero turned the whole affair into a witch hunt and forced Catiline down the road he eventually took.