I've never used twixtor, I've seen those amazing 1000fps DSLR videos.
I have done some similar things in after effects Timewarp with mixed results.
Does anyone know the difference between the two options?

Is twixtor anything more then Timewarp at maxed out settings?

Interesting question!
(I was just looking for the AE equivalent of Optical Flow and learnt it's Timewarp.)

I'm curious about any reaction on your question.

I use Twixtor all the time, but rarely for slowing things down, only for speeding them up. (Primarily 30p to 24p) Anytime you are adding synthetic frames, the concern is abnormal artifacts. When you are removing frames, there is less chance of that. I use Twixtor to slow things down as well, and while the results are better than any other solution I have found, they are by no means what I would call perfect. My footage is pretty intense, so the motion estimation engine frequently miscalculates. I find the most issues near the edge of the frame, especally when the camera is moving.

The Foundry recently released a plugin called Kronos, that you may want to look into as well.

Both are good, I the twixtor workflow takes longer but I reckon the results look better.