My game (PC) version is on 1.02 I want to get the free dlc's but that requires me to update, due to server unresponsive issues I downloaded the actual patch installer that takes you straight to 1.08.3, the game is running fine now and have not encountered any bugs that I could not fix, question is should I update the game?

If you want to be on the safe side install GOG Galaxy and import the game to it. Enable “Receive preview updates” in Galaxy to get Galaxy 1.1 now (it has a rollback feature). Install the patch. If you have problems with patch 1.08.3 just rollback.
http://www.gog.com/forum/general/gog_galaxy_first_major_update_available_now_d6369

== IMPORT ALREADY INSTALLED GAMES TO GALAXY ==

For GOG games installed using installers from the last few months (so called Galaxy-compatible installers)
Click the "+" button on top of the sidebar and select "scan and import folders" - it will find all compatible games within that folder and add them to the Client.

http://www.gog.com/forum/general/gog_galaxy_beta_2/post1

Hard to say. Some people have had problems and some haven't. I have had less problems than others.

Personally, I would update just get rid of the mutagen slot bug. You won't notice the bug normally. It renders your mutagen bonus inert after loading, unless you unequip the mutagen and re-equp it. Quite annoying.