The Match XP Beta is incredibly "essential, " which is not bad, but you get XPs on a few events, like either if you win, you’re first in your team, or/and you completed the game. Maybe I would add mini-quest completions that may make the list higher.
I am unsure if you will ever include XPs gained by medals received (probably for the Spartan Career you are building), but I wouldn’t mind if you get the total points you made in the game as XPs.
I understand that the points in the game have usually 4 digits instead of 3 from the XP, this is why I think you should add one more digit to Challenges and XPs received. Not only you can turn in-game points to XPs, but also I think 4 digits make the total XP number bigger and, I think psychologically(?) appealing as if you have made a lot in the game.
Speaking of UI, I would make the list of XPs received “pop in” one by one and briefly shine, so that the list of your XPs isn’t as static as it is now. Also, I think you hear one sound effect that comes from how the XP system used to work before the winter update that does not match how it works now. It’s as if there is still the old system working behind the new one.
Overall It’s not as engaging as in MCC or Reach, but it’s definitely something.
PS: (also thanks for keeping the 500 bonus per day, It encourages players to play at least one game)