Oathbow any good?

[Undone]

25,600 gp +2 Comp bow Rarely +5 with +2d6 (Equal to a +7 bonus).
32,000 for a constant +4.

Is oathbow a good buy?

[Imbicatus]

Oathbow is great for killing bosses. Not so good for killing everything else. It depends on your campaign, and if you gm favors one really tough fight or multiple smaller ones.

[Claxon]

Not particularly. The restrictions basically make a 1 combat per day sort of item, and then still it's only good against 1 opponent per day.

Considering the cost of the item, it is better to simply buy a regular +4 bow for slightly more. You get 70% of the benefit, but against everyone.

Personally I would never buy one simply because you'd need a back up bow to be effective against other creatures, and if you have to invest in a backup weapon you might as well just make that your main weapon instead.

Sure, you could be extra awesome against one guy per day. Is that worth sucking against everyone else?

Also, keep in mind that if you do have a single enemy fight, it usually doesn't matter if you're a bit stronger against that one guy because action economy is so heavily in your favor already. However, when there are multiple enemies and multiple encounters....wellll....no bueno.