I'd like to add an interesting magic item, particularly for Manyshot users and Splitting Bows.
Glove of the Master Strategist from Ghostwalk.
it functions as a Glove of Storing, but once per day allow you to use a True Strike effect.
The kicker? they only cost 3,600 gold, and you can wear two.
The Splitting property copies all bonuses and penalties from the first attack to the second, including True Strike. Manyshot fires two attack rolls with one arrow.
With both, the True Strike effect will give you effectively a +20 to four attacks, per glove, as well as giving you somewhere to store that cumbersome bow where it's not noticeable.
Also, on Factotum Archer builds, personally i'm a fan of going at least 11 levels of Factotum for Cunning Breach. 2 Inspiration Points to ignore the targets Damage Reduction and Spell Resistance for 1 round. There are cases where ignoring the targets ability to ignore your damage is better than throwing more arrows at it.