Did some updating of the original post with my most recent build. Moved to using a reach weapon instead of a curveblade, and squeezed a few new feats in there. I still want the character to focus on critical hits and tripping to be his tricks in combat, as those sound fun and effective.
I'm not sure that tripping works well at higher levels. I think the CMD of enemies tends to increase faster than your CMB will. There's also the problem of more flying enemies (immune to trip), more options for multi-legged creatures (harder to trip) and more options for creatures without legs (immune to trip), more creatures that are at the high end of the size scale (can only trip 1 size larger than you)
So I'd be a little cautious about how much investment I put into trip attacks versus normal combat.(note that I'm not basing this on real high level gaming experience with a trip monkey and a lot of it is campaign dependent)
If you're going crit focused I do recommend having Critical Mastery and a couple more of the crit modifier feats, Crippling & Bleeding aren't bad options as Bleeding is available early and there's a feat that allows you to apply 2 of the critical feat attacks on 1 crit.
Weapon Spec is an okay feat, but honestly I'm not in love with it. There are lots of other things that just seem more effective than doing +2 damage per hit. Maybe I will pick it up at the higher levels when I start to run out of interesting feats to take. Although at higher levels +2 damage seems even more irrelevant.
The feats Weapon Focus, Greater Weapon Focus, Weapon Specialization and Greater Weapon Specialization together add up to +2 to hit and +4 to damage on each hit.
One of the things about the optimization game is that you're often better getting lots of little bonuses rather than trying to find 1 big bonus because they do all add up.
At the level you can get Greater Weapon Specialization you'll commonly be hitting twice a round (3 times with Haste) and with a reach weapon attacks of opportunity aren't rare so you can commonly be putting out an additional 12 - 16 points of damage a round. That adds up over a couple of rounds.
Basically the bonus to damage is the same as the Barbarian gets as part of their level 20 ability
I have to agree with Ramaster. I don't feel power attack is very useful at low level. Many enemies tend to have an AC in the range of 14-18, and my attack bonus is only going to be +5 at level one. I hate power attacking if I think my hit chance is going to fall to less than 60% or so. Plus, with trip being a focus of this character, power attacking directly lowers his CMB, and makes him less likely to successfully trip for that round.
One of the upsides of the number of feats that a fighter has is the option to build multiple trees, so you can have power attack for when you don't want to trip, you've already tripped it on an opportunity attack or it's immune to trip. There's also a feat that negates the penalty from power attack on your first attack for the round so you could trip the enemy with that and then beat on it once it goes down.
At first level I think it's probably best as a prerequisite for Cleave which gives you a fair chance of taking down 2 enemies in a round (60% to hit gives 36% chance of hitting twice)
Note that at low levels you go from an average of 8.5 to 11.35 damage on a hit by turning power attack on with a 2 handed weapon for -1 to hit (based on your current stats, weapon choice and feats with combat expertise changed to power attack)
Which gives you a much better chance of taking down a Lizardfolk, horse gnoll etc in 1 hit.
Power attacking gives you more average damage per hit for your character unless you need an unadjusted 18 or 19 to hit. at AC 18 you'd need a 13 to hit normally so you go from 3.4 to 4 average damage per hit. and there's only 1 in 20 chance of missing due to the power attack.
(Things change at 4th level due to the penalty going up 1)
Of course you do have the penalty to hit and it reduces your chance to trip on Attacks of Opportunity
It looks like the rest of the party is shaping up to be:
Paladin (Warrior of the Holy Light)
Summoner (Synthesist)
Rogue
Cleric
Interesting party composition.
If the rogue isn't a ranged rogue you'll want to be paying attention to setting up flanks with the rogue because with the reach you can threaten a lot of creatures. Against that if they move into an adjacent square you stop threatening so the rogue can't flank with you. Of course that also means they probably aren't attacking the rogue so...
It could end up with you having a party of 5 melee combatants which makes your control less effective (because if everybody wants to move up and attack then you get a lot less attacks of opportunity and the battle becomes more static) Of course tripping something that is surrounded by your allies gives them big bonuses to hit and once you get Greater Trip then they all might get attacks of opportunity...
