Timing seemed pretty perfect to me. I'm not the best reference, but all the beats were where I expected them to be.
These are pretty perfectly mapped. Only thing even remotely worth changing is that the reverse sliders at 53:40 "bounce" at a time that isn't synced to anything, so maybe you could consider replacing them with regular long sliders. But that's a minor, minor thing.
Also, are you considering making a hard version? I realize that this song doesn't really need one, but you've done a really good job syncing beats to the background music rather than the lyrics, and I think you could keep doing that for a pretty compelling hard mode.