This game has a lot of "follow-me" quests where you have to tail an enemy without getting detected. I hate these quests, even more so when you are put under pressure because of a countdown clock.
I recently completed the Micheletto Corella quest which has you following him to various Borgia strongholds to recruit soldiers into assassinating an actor during a play at the Colosseum.
It helps to use your trained assassins to take out the soldiers, whilst avoiding being detected by any other Borgia guards. The Colosseum part of this quest is very difficult, you have to scale the building without being detected by any guards. Once you have made it to the checkpoint, you have a countdown timer to assassinate 4 Borgia snipers. After this you just need to play your part in the play & then attack Corella with your hidden blade.
Completing all the Leonardo Weapon side-missions rewardw you with a Parachute you can deploy by pressing X when jumping off a high building, useful for doing air assassination kills.The game has quite a few side missions & challenges which you should really complete to unlock special items & weapons. I managed to unlock the Sword of Altair by completing all the assassin guild challenges, this is easily the best sword in the game.
Having just completed Sequence 7 & I could very easily rush through the game and complete the remaining few sequences but there is so much still left to do in the game from the Shop Quests, Guild Challenges, Romulus Lairs & I have not even started the gylph puzzles.
My plan was to finish this game over the Easter break but I think I may be playing it for a while yet.