Is it worth it to install the patch that allows you to do all the quests and get all the strongholds or does it spoil the game?

Of course it is cheating, but if you won't start up several games to try out each stronghold go ahead.

It does spoil the replay value of the game a little though.

<font color="gold">If I were you, I would first go around a couple of times, and then start using patches that makes the game more fun. This is to get a maximum gameplay-experience. ;) </font>