I have now updated to PR1.3 via OTA.

[Before Upgrade]
Had multiboot setup as following.
1. Original omap
2. Power kernel v40
3. Nitdroid

Had it booted up using option 2.
Had it overclocked to 1Ghz.
Had Conky as Live Wallpaper
Using Black Plastic Theme
Had Theme Customizer with smaller desktop icons.
Had modified hildon desktop with enlarged thumbnails for multi-tasking
Had many many many apps installed.
Had MSCIM with Hangul (Korean) IME.
Had Swappolube with propsed settings enabled.
Used FAM to upgrade to PR1.3. (not HAM)
It told me 1022 items will be upgraded. ~85MB.

[After Upgrade]
It took around ~20mins to upgrade.
Didn't prompt me to reboot. Did it anyways.
Now About Product shows the new version.
Noticed my icons on desktop are back to default size.
(update - new version of theme customizer fixed this issue)
Still booted up to power40 kernel without issues.
Overclocking still works. Back to 1Ghz.
Live wallpaper works.
Modified hildon desktop is not working. (haven't tried reinstalling yet)
I STILL have multiboot. I can still boot into Nitdroid.
Swappolube shows that it has reset the values back to default.
I still have issues with video recording dropping frames. Grrrr.

[Things Noticed so far]
MicroB bug of address bar buttons not appearing STILL exists. Grrrr.
MicroB seems smoother during scrolling pages around. Maybe maybe not. lol
Transition effects seems smoother. Dunno It just does. Drops less frames.
Multi-tasking seems a bit snappier. Hmm. Maybe due to smoother transitions?
Overall, upgrade went smoothly and didn't really make anything worse. Good enough.

Now where's PR1.4?