Scurvy_Platypus
Explorer
What are your thoughts on giving the PCs and action point each day as opposed to a pool you get each level?
By day do you mean per rest? I would recommend against it. First off, there are going to be battles where players are going to want (and need!) to spend multiple APs. And actually, that's kind of the point. APs are meant to be another resource that the DM can chip away at to challenge the players. If they refresh after a rest, that component is removed.
Hit points are meant to be a short-term resource; APs are a long-term resource.
On the other hand, I happen to think that Action Points refreshing per level is complete bleh. I'm a fan of them being a per session resource and would say they should start at 3 or 4 points.
It should be noted that by doing this, you're shifting the game into a more actiony sort; some people would call it "heroic" but I dislike that term. You're already playing "heroic" characters in theory. But having AP that refresh each game session means you can expect to do a certain amount of things fairly consistently.
I'll also note that I'm a lone voice advocating this.

My own experience has been that AP that refresh per level are generally forgotten and hoarded until the end boss fight. This is a playstyle thing and therefore not everyone will experience it, because not all GMs run games the same way. However, for the GMs I've had that tend to have the big bad boss as the final thing before leveling up? Oh hell yeah, people hoard them. Throwing tougher encounters at people in an attempt to trick them into using their AP or to "encourage" them to use them doesn't really make much of a difference.
The big thing to think about is, what function are AP serving in your game?
Spending 1 AP every 2 or 3 encounters is... well, looking at what AP can do, and thinking about the fact that you can only do one of those cool things every couple or three encounters on average, you need to decide if that's the tone of the game you want or not? Do you want your Fighter to be able to auto-confirm a crit with an AP once every 2 or 3 encounters? Or do you want him to potentially be a whirling machine of death (well, for 3 or 4 critters

Don't forget about the casters though. Switching to a per session method means that Restricted spell slots are going to be recoverable far more frequently, and Ritual spell slots as well.
And of course, people can be spending them to recover the HP more frequently as well.
Certain things like the Bound Item use *(spend an AP to Bind an item and have it improve as you level) are going to change as well. Now, you can leave it as is, in which case some folks might feel it's "too cheap". You can go a different direction and have it reduce the character's per session AP by one, in which case it might be "too expensive" (and you might want to be running with 4 AP per session if you're thinking of going this route). Regardless of which direction you go, it's going to have a bit of a different effect and you'll want to think about whether you're fine with that or not.
No bones about it, AP are a _metagame_ resource. Use of them has an _in-game_ impact and you need to figure out _what_ that impact is and if messing with them is going to impact your game the way you want. It _will_ have an impact. For the kind of games _I_ like to run (high action) it's a good thing; if you're wanting something "realistic"/"gritty"/"sword & sorcery", then no it's going to have a negative impact.
In my game when I did AP as a per session resource, characters were definitely more dangerous. I didn't have all the tweaks and stuff that Trailblazer has with AP, but I found players tended to be more aggressive in their fights because they had the AP pool there to pull their bacon out of the fire or to spend to help them shut down an opponent hard. Because the players knew it'd be refreshing the next game session, they didn't really spend a lot of time hesitating about whether or not to use their AP. The resource management they engaged in was at the session level, as opposed to the "string of encounters" level.
For people that like screwing around with mechanics, there's some fertile ground out there in terms of how many AP are given, how many AP are given when they refresh, and how frequently AP refresh. I think Trailblazer takes a "middle of the road" approach generally, although my sense is that Wulf and GlassJaw tend to lean in the direction of "gritty" as opposed to "action hero".
I know I sound like a broken record but I can't emphasize it enough: Know what it is that you like in running a game and try to have as clear an idea as you can about what you _want_ in the game. It'll make things much less painful for you when you start pulling and poking at mechanics.