I've just had a 'post-1.49-update' go at this race in the McLaren 650S with my usual 2-stop RM strategy. I finished P3, 8 seconds behind the leader, which is pretty dire for me! My best lap was a 1:58.0, which again is bad for me.
The most noticeable differences (post-1.49-update) were (1) tyre grip, (2) tyre wear, and (3) the AI drivers. The tyres lack the level of grip they had before the update, requiring a lot more finesse on the pedals, and often a very slight lift to prevent running off the circuit during fast bends that didn't concern me before. It's been a while since I've been racing IRL but I'd say the feeling is much more realistic than before. Where you just used to hang on, knowing that you'd get round, now the lack of grip as you exceed the grip threshold is quite noticeable - I ran a little wide a few times, although I was always able to recover things before going too far. I'd say that racing 'on the ragged edge' is now a big part of almost every bend, and the level of focus required is way more realistic than previously.
Unexpectedly, I didn't have a problem with oversteer during fast exits. On the couple of occasions that the back did get loose, I was able to recover in microseconds without any drama.
The RM tyres show less 'red bar' wear than before the update, but the actual drop-off of performance is more gradual and more severe. I used to be able to ignore the tyre wear until Lap 8 in any given stint - now it is very noticeable from Lap 7 onwards. I really had to lower my corner entry speeds in order to get round some bends on worn tyres, and I'm sure that affected my lap times quite noticeably towards the end of each stint. From what I could see, the AI cars suffered from the same issues.
The AI drivers are noticeably different, being a half-way-house to full-on Sophy. I used to overtake cars and forget about them; now they fight back and sometimes recklessly so. I did (and finished) the entire last stint with Rubilar right on my tail, and he coped with the back-markers effortlessly. The AI drivers are now way more realistic, speaking as an ex-racer IRL.
Overall, a more challenging race, and one that requires even more focus than before the update. I've only done the race once since the 1.49 update but I didn't have any 'offs' or penalties, which is a good start. I think my main issue now is to try and get my laptimes back into the 1:47s again, which I'm guessing is going to need adjustment of my entry speeds ...slow in; fast out, as we used to say.