I don't like the Octobrush very much. I didn't use the Inkbrush much, so maybe my thoughts aren't worth much, but here are a squidiot's musings:
This doesn't feel that fast. The run speed isn't so bad - it's no Inkbrush, but it's still kinda speedy - but I don't like the swing speed. It's just a tad slower than what I'd like it to be, and it's kind of annoying. But this isn't so bad, I knew it wouldn't be Inkbrush-fast, that in and of itself would be okay given the extra range and power it has.
Speaking of which, the range on this thing is surprisingly good, and the power is nice too. It's not going to outrange most guns, but I don't think it's supposed to, so that's alright.
The loadout is where it falls apart for me, though. Squid Beakons are a decent sub, they're valuable for supporting your team and in a pinch you could maybe form a makeshift barricade with them, but they just don't work with what I feel like the Octobrush is supposed to do. It's an Inkbrush for fighting, or at least I see it that way, so Squid Beakon might be the worst possible sub for it to have (as much as I'm not a fan of Point Sensors, at least they're good for spotting enemies and potential ambushes, which is something more than Squid Beakons can do on offense). The Kraken, while capable of attacking, isn't a good solution to the problem of enemies who are outside your range either, for three reasons:
A) It has almost no range, you have to touch opponents with your jump to splat them.
B) You can be pushed back by enemy fire, preventing you from reaching your target.
C) What do you do when you don't have Kraken charged and can't get close? Drop a Beakon?
So it's not much good for offense. Really, the Kraken is best used as a panic-button to escape from situations you can't fight your way out of (since it's invincible and doesn't have to worry about enemy ink, and it's not like they can stop you from running away unless you're getting pincer-attacked) or to surprise opponents (since it's pretty fast and can quickly reach areas you might otherwise have to spend a second or two inking to swim up), of which the former is actually really useful for a close-range weapon and the latter can be kinda nice at times but isn't strictly necessary for it to function (and as an Inkbrush offshoot, it can already do that fairly well, I think).
Overall, this thing could be good, but it needs a bomb-type weapon of some sort, or at least Disruptors, just something other than Squid Beakons. And it would be nice to get a special that isn't the Kraken, preferably Bomb Rush (or Bubbler if it gets Disruptors, I feel like that could be an alright combo), but that isn't really required. Right now, the current Octobrush is usable, but hardly optimal.