I’m excited to see the new patch 1.5. It’s been awhile since I’ve played, so I’m looking for some input on what changes I’ll see from recent patches in current save game files vs. what i’m miss out on from starting a new game. Can someone from warhorse comment on if most of the bug fixes and graphics optimizations work with old save games?
Yes, you can use old saves 
Saves from previous versions are compatible with patch 1.5
Interestingly, when I loaded any of my saved games after the latest 1.5 patch, I got not only the “lost & found” quest, but also the objective “Find the cave in the hills near Ledetchko”, which I couldn’t find in any of my active quests.
I played some last night, and even on old save files I am happy to report a noticeable improvement. No crashes, little to no texture pop-in and solid FPS with almost no screen stuttering. 