It's a 25Mb download.

edit: Horses seem...different. Not 'bad' different, just different. Looks like some work has been done on the horse control, i.e. turning while galloping is now slower (I guess to make it a bit more realistic).

edit 2: patch 1.7 was 27Mb, so patch 1.8 is smaller! It makes you wonder what has been removed from the previous patch. Would have expected it to be a bit bigger, considering it (most likely) contains information for Dragonborn DLC. Still, if the patch is simply optimized which reflects the smaller size, then this is good as it means a couple more Mb of memory has been freed up for use by the game. This helps to reduce stuttering as the game doesn't need to swap in and out data to the HDD as frequently.

Horses nerfed? I will be sure not to download this patch until the patch notes convince me otherwise, which I see nowhere on the forums yet.

The horses aren't broke as such. They just feel a bit different. I don't know if you saw the Beta Patch notes for the PC, but there were threads discussing changes with the horse control.