It's very good, definitely an improvement over the first Shift, it's a bit tough to describe because they've made a lot of improvements:
1. Menus and navigation is faster, more responsive, loading times are better in general, the new music is also pretty good.
2. Graphics and effects are better, however my CPU (E6600 @ 2.8GHz) bottlenecks and it gets stuck at 25-35 fps which isn't enough to play it smoothly, you will need at least a stable 40 fps, preferably more.
3. Crashes, spins and sliding are more realistic.
4. There are more real tracks, they often use parts of the track (It's enough to say that your first races are on Suzuka and Monza)
5. There are more cars and all the garnish with upgrades, vinyls and so on, but no1 really cares about that.
However, my biggest issue with the first game was steering delay (with X360 gamepad for PC), it's still there and it makes for some very frustrating driving errors especially with unstable fps count. You can tweak responsiveness and deadzone settings all you want, but it feels like the car starts to turn well over a second after you move that d-pad.
Also in cons is the cheesiness of the "story", if you can call it that. Experience points for mastering corners, following racing lines, overtaking, speed traps, - that, combined with awkward instructional/narrative of that Racing Driver they made the game with just feels corny. They could have made it a simple scheme of Win -> move on to the next event - and it would be a lot better.