That 'early days' is the big part though. No one will have burned trough their 100 passes yet. Even if you have to use them Monday through Friday only, you'll be out of them by mid-March (assuming no days off) so we won't know the true impact until then.
I concede that for a fair number the CC will be massively beneficial. I took a bus at the weekend through St Clements and there was very light traffic there and certainly none of the slow moving tailbacks I'd expect to see there. However, these schemes rarely see people suddenly all jump on buses, bikes, scooters and walking especially if those options aren't open to you (eg, you drive to work out of the city, your route is poorly served by public transport, the roads aren't designed for cycling or walking on). The traffic may have gone from the CC areas but it's simply moved elsewhere.
My perception is that the Eastern bypass (always slow in the evenings towards Littlemore) has a lot more traffic on it in the mornings and evenings now in both directions. That may be by design since the strategy is to have fewer cars travelling from A to B in the city itself. However, I can see this essentially making the ring road, A34 and approaches to the A40/M40 even busier.
To me, there are still better options out there than this.