Performance is superb. It's the crashing that's absolutely killing the game for me. I can't get into it. Having to constantly save to avoid losing progress.

I also noticed a drop in fps (5-10) so I deleted all user config files and let the game recreate them.
After that I set all to low and then upped everything to ultra except foliage and enable everything but hairworks and vsync.

Putting all to low and then manually up the values to ultra helped me to get +5-10 fps with patch 1.02 (a hint I gathered in these forums) but it seems it didnt work this time though.

I now tried to enable hairworks to see how the performance is and then disabled it again (better performance than with 1.02 but still loose too much fps using it) I also enabled vsync now and it seems I have the "lost" 5-10 fps back.

You might want give that a try (I have just checked the fps where I currently at though --> Velen banditcamp to the right from starting point) and I am back to +40fps!

Edit:
It only worked near that Banditcamp :(

I verified that I had better performance before by installing the day-one patch (1.02) over 1.03 and got better performance without changing my config.

I also tried to set MaxTextureAnisotropy=8 and MaxTextureAnizotropy=8 (no idea why two of them exist) because they mentioned that they raised Anisotropy to 16x on Ultra but it had no impact on the performance (checking with fraps).

System
Xeon 1245v3
16GB RAM
R9 280x (Gigabyte Windforce 3GB with GTA5 Beta Catalyst Driver)
Win8.1 64bit

Good news is that patches are optional, if you got better performance with 1.02, you can stick with it.

You guys understand that they've added more detail, right?

Boosted texture anisotropy sampling to 16x on Ultra preset
Sharpen Post-process settings extended from Off/On to Off/Low/High

16x AF wasn't even in the game before. Ultra now has twice the detail as far as terrain detail is concerned.

(Just Scrolling Trouight

AF has next to no framerate impact on modern hardware. Maybe 10-15 years ago you'd be right in thinking it reduced performance by any significant amount. It also does not magically increase detail, it only makes textures look clearer when viewed from an angle. As far as I'm concerned, 16xAF is a baseline for 3D game graphics that has no reason to be disabled, so the patch is only bringing that up to expectation.

Actually I feel as I have less fps too... Its about just a slight drop, but
1: it feels choppier even with ~55 fps. I was amazed how fluid the game felt with 40ish frame per second... now it feels less fluid even with higher fps.

2: I had stable 60 with 1.02 with my current settings

3: with sudden 180 turns, there is a slight drop (and the game is on ssd, so no texture load problem)

same, about 3 to 4 frames, but I am now upping a few more visual settings to ultra and the fps remains fairly contents (some settings I have left at high, because I see absolutely no change graphically, so why bother), happy :) HBAO+ on and HairWorks still on

edit:
No choppiness at all and things are still fluid, so no idea what/s going on there.

My performance in game went from enjoyable to almost unplayable. On 1.0.2 i got some occasionaly freezes but on 1.0.3 it's almost constant stuttering. I had to remove the game and install it once again to go back to 1.0.2. I hope that there is an option to rollback to patch of our choice in the future. My system is quite bad but on 1.0.2 the games looks amazingly good for such low spec.
Edit: forgot to add that after the patch even the menus were stuttering and the game didn't close properly - sound from the game keep going after exiting and the game process was still up

My system :
Intel Pentium G2130 3,2GHz
Radeon HD 7770 1GB
4GB ram

I'm pretty sure you're short on RAM. That'd explain the stuttering.

i dont think i can play after this patch tbh, i get crash every 2-5 minutes...nothing changed except now i use xb one pad & the game was patched. but i am on windows 10 so i have to put up w/ it i guess, fortunately soon win10 will be official

I had same or slightly improved performance after installing the 1.03 patch, played with it for a few hours. After closing the game and starting it again later my fps is down from 60 to 20s. Interesting, very interesting.

Edit: Reboot fixed it for me. Might've been a software issue on my end.

I'm running i7 4770k, 2XGTX 780ti Superclocked and have everything maxed except for hair off and foilage to high and I got a solid 60fps @ 2560x1600 with dips down to 57 sometimes. This is running latest patch and drivers.

That ones easy to explain. You have blur on. It's working as designed. If you hate it turn blur off.