I've been trying to delay going to Hearthsong, knowing what a bear it's going to be while this problem persists. Hoo boy...
In the interest of bringing more attention to this issue, I'll post my own savegame and info.
Savegame
Here's my latest savegame. (Uploaded and shared through Google Drive; if there are issues, I can find another hosting service.)
System Specs
AMD Phenom II X6 1090T Processor, ~3.2 GHz
Windows 7 Professional
16 gigabytes RAM
Game installed on SSD, Windows installed and savegames located on standard HD
Description
As with the original poster, starting at around 20 hours of play time, the process of saving games and loading new maps began becoming increasingly lengthy. Quicksaving now takes around 15-20 seconds to complete; transitioning to a new area takes 30 seconds or more.
As a temporary measure, if the problem is too complex to resolve in time for the patch this week (or unable to be replicated at Obsidian), I would suggest enabling an option to turn off autosaving after map transitions. Saving will still take much longer than it should, but at least navigating the game will be less frustrating for those of us experiencing this problem.