Perhaps not, but it significantly ups your odds of an unreliable one. 1d20+0 will hit a DC 10 check half the time; 1d20+3 makes it closer to two-thirds. I prefer for my character to have at least a chance of contributing in a lot of situations, and just generally seeming like a well-rounded individual, instead of being a one-trick pony who's dumb as a box of rocks (unless being dumb as a box of rocks is a part of his characterization, rather than just a consqeuence of not having any skill points).A +3 is not going to matter much in most cases. If you haven't already invested in that skill, it's not going to get you a reliable success.
There are many checks for which a masterwork tool doesn't make sense, and others for which it's overpriced (Alchemist's Lab being the obvious example, but even Climb costs 80 gold rather than 50, and that's a big deal for level 1 characters unless the GM is generous). Plus you can stack Skill Focus and the masterwork tool, and ranks and an ability score. Maybe there are other sources of bonuses in books I haven't read, but at least in core Skill Focus has utility for helping your check hit an absurd bonus at the early levels.And if you are investing in that skill, there are plenty of ways to boost it. Masterwork Tools are 50gp a pop for a +2.
Being able to full-attack is not something you can rely upon in my experience. And precision damage only matters to a handful of classes. Multiple attacks as a standard action is danged impressive according to everything I've seen (which is admittedly not much compared to professional optimizers, or even people who get to play every week for a year or so; I am sadly not one of those people).The attack penalty on Manyshot is simply too high. The range is too limited. And because it's a "volley", you can only apply precision damage (Sneak Attack, Skirmish, Favoured Enemy) once. Manyshot is not a good feat, and it becomes worse as you level and your full attack routine improves in comparison.