I tried this mod last night (the Origin one) and I must say that I noticed a significant difference. I used the default settings. Switching between lots was much faster as well as load times even on my largest lots. I did notice a bit of lag when my sim was running between lots but I don't have a top of the line PC and I have all my options on the highest settings. Panning around the world in map view was a joy with no lag at all.
Buy and build mode showed the most difference. Patterns loaded fast and I was able to quickly recolor objects as well as turning the camera without noticeable lag. I didn't try creating a sim but from what I've seen on the videos, that is supposed to be improved as well. I will try that out today. I used this mod without any of my custom or store content and will add that to my game and see if it helps with all the added junk I have. I didn't notice the music stopping as mentioned by Kelvin and will keep my ear peeled for that.
@Onverser - according to the mod creator - "that error can be fixed by increasing the “Delay” value in TS3Patch.txt, around 500-1000 should work!"
I think this mod is a game changer!