I've already made my opinion known on Shield Training in another thread where I think it is outright obsurd that it is the only way to make taking off or putting on one's shield an object interaction and despite this be so heavily only useful to spellcasters as a feat. We should not be in a situation where a wizard with a few weeks of training weilds a shield better than a fighter with a life long commitment to martial training because they (rightly) did not want to spend an entire ASI just to take their shield off quicker.
I LOVE CHEF. Even if it does sort of severely undercut a certain popular 3rd party Chef class I like. I wish it could give expertise to those with the proficiency already though.
I also feel like the martial training one is a tad weak. Fighting styles are nice and all, but even that classes that get them all get another feature at that level. It should be a fighting style and then +1 to str, dex, or con.
What I've homebrewed (and will still be using) in the past is to combine all the weapon/armor proficiency feats and give the player two of four options:
1) All weapon proficiencies
2) All armor and shield proficiencies
3) +1 to strength, dexterity, or constitution
4) A fighting style.
I go back and forth on the warlock invocation feat simply because I think 1 invocation is definitely too weak, and 2 invocations might be too much. Maybe tack on another +1 to a mental stat?
My main issue with the metamagic feat isn't the feat itself. It is nice. It is that it is yet one more thing taken from sorcerers and effectively given to wizards or other casters. But that is a discussion well commented on and is a larger issue than simply adding the feat itself.
Poisoner is a feat that I love as well, particularly because the resistance ignoring effect as written also applies to spells. Yes, it could already be gotten by elemental adept, but this feat I feel is so much more flavorful if one wants to play say a crazy poison obsessed swamp witch.
The final feat that is a tad frustrating for me is the Tandem Tactician feat. It is a great feat that I think is long overdue to exist. The frustrating rub for me is that it is not only outright as good or better than the Mastermind Rogue's primary subclass ability, it doesn't work with it either. This is perhaps more a critique of the mastermind rogue being a seriously flawed subclass in general (despite being such a core sort of rogue in fiction), though at least before this feat one could make the arguement that their higher level abilities being kind of "meh" was at least outweighed by having lower level awesomeness. Not so any more after this feat, pretty much take assassin or swashbuckler and this feat + actor and you're basically better than the Mastermind at...masterminding. Wizards really needs to reevaluate their stance on doing additional rebalancing passes on their already published content. sigh