Alrite so I went hunting for a shiny/uber Growlithe on route 8 and decided I'd test out the new catch rate. What I did was for one Growlithe, I would throw pokeballs leaving it at full HP and record how many it took to catch it. Then on the next one, I would lower its HP to roughly 25% or less. I did this for 10 Growlithes, 10 Vulpix, and 16 Abras. Here's the data:
Each asterisk indicates 1 ball thrown. I used asterisks instead 1,2,3, etc. to help in visually representing the data.
Growlithe:
---- FULL HP
***
**
**
***** **
***
--- 1/4 HP or less[/i
*
***
*
***
***
Abra:
---- FULL HP
*
***
*
****
*****
***** ****
*
**
---- 1/4 HP or less
*
*
*
*
*
*
*
*
Vulpix:
---- FULL HP
**
****** *
***
***
***** ***
---- 1/4 HP or less
*
*
**
*
***
So for Growlithe, it took an average of 3.4 pokeballs to catch at full health versus 2.2 at low health. For Abra, it took 3.25 pokeballs at full health versus 1 at low health. And for Vulpix, it took 4.4 pokeballs to catch at full health versus 1.6 at low health. Of course, the amount of data isn't extremely significant, but I think it's enough to show that it's working (especially with the catches on Abra). I also want to note that in the time catching pokemon since, it seems the more I lower their HP the greater the chances of catching, which is good cause that's the point right? Anyway, hope this helps.