Um. It's really hard to gauge. Technically they didn't do anything? No actual law was passed, nothing legally binding, just a voluntary appeal for the Catalan government to declare independence and issue decrees to start putting it into effect if it wanted to, but they did neither. Then nothing at all was published on the official gazzete of Catalonia, so, um, if you just look at the law, really, nothing has changed. It's just that everybody decided to wink at the same time and call it a declaration of independence.
What has actually happened is that the national government took over the regional administration, fired the cabinet and called for new elections. The police and the courts accepted it without hesitation, they control the Catalan budget and tomorrow an envoy from Rajoy is going to walk into the Palau de la Generalitat (a Spanish flag is still flying over it) and present himself as the new boss. The civil servants are expected to obey (or else will be fired) and nobody expects any of the deposed consellers to actually walk into their offices lest they be arrested for "impersonating an authority".
There will be regional elections in two months, organised by the central government, and the independentists have to try to come up with an excuse to contest them because even they understand that, well, this is where the power really is. They have 8 days to announce a repeat of the coalition they did in 2015 and everyone sort of wants to repeat it (because you always get a couple of extra seats if you pack up the votes into a single party, even if all four constituencies give enough seats for D'Hont to be pretty proportional) but nobody wants to because the three independentist parties hate each other, and they aren't supposed to be even talking about that, because in their own parallel universe, they are an independent republic and why would they be contesting an election organised by a "foreign" government. But as one of the secessionist deputies said, "the Republic isn't a real thing, but a state of mind".
Polls expect pretty much the same results from the last three elections to repeat: the independentists on 47-48% of the vote but with a majority of seats due to overrepresentation of rural, nationalist zones at the expense of (pro-unionist) Barcelona, but some point at the nationalists losing their majority if they split up, at which point all bets are off as to what kind of government there will even be.
I just want to know what will happen when those hundreds of thousands of people who believe something did happen on Friday finally find out that... actually nothing did... and that we are back where we were in 2015, except with more anger, more division, more disappointment and a wrecked economy.