So I played a fighter in the Gen Con playtest this year, and I have a few suggestions for gameplay improvements. as a result of my experience.
First, something needs to be done about diagonal movement. Discussion over how it worked ended up slowing down the game far more than it should have. I would simplify the "1.5 squares every other square" rule to "for any movement during which you move diagonally, treat your movement speed as 5 feet slower."
Second, the wording on the grabbed condition seems needlessly complicated, and it forced us to stop and look up what exactly it forces a check on. For clarity, I would suggest putting a table somewhere that lists common manipulate actions and activities. An increase in the flat DC would be handy as well (6 seems appropriate, with a 25% chance of failure being fair for those who are committing themselves to a grapple).
The third thing is minor but could use clarification: is it intentional that the break grapple action is affected by Armor Check Penalty? I could understand why mechanically and reasonably, but I want to be certain.
A fourth thing may be viewed as a tad powerful, but I think it would make sense for the flat-footed condition to impose a -2 penalty on saves in addition to the penalty on AC. Unsuspecting foes would logically be more vulnerable to mental effects and explosives, and mechanically I think there should be some incentive to grappling an opponent before shoving or tripping them (or, if the players feel particularly frisky, holding them while a fireball goes off on top of them).
Finally, I enjoyed playing a 2e fighter a great deal, and felt that I had a lot of functional options to work with (more than I ever did playning a 1e one).
Diagonal movement is identical to how it works in first edition. 5 feet, then 10 feet, then 5 feet, then 10 feet, etc. making all diagonals cost 10 feet is too punishing and defeats the purpose of diagonals.
Perhaps I mistyped. What I meant is that any move action where you move diagonally would be at -5 speed. For example, a character with 20 feet of speed could move 4 squares laterally, 3 squares diagonally, or 1 square diagonally and 2 squares laterally.
So mechanically if you start calculating distance differently for movement than range for spells you get into a bit of trouble for spell templates and range rules.
I believe that the rule is fair. Math on it breaks down like this:
Assume speed 30
If you take all 30 as diagonal movement currently you go 4 squares.
4 up and 4 left this calculates out to 28.28 feet round it up and you have your 30 feet of movement. It is as close as you can hope to get off of a simple rule which is why it was not modified between versions.