I use xp to track levelling and award xp for encounters defeated, quests completed, and great ideas. xp for encounters is generally easy to calculate, for the rest I typically award an amount of xp needed to reach the next level in increments of 2.5%/5%/10%. Completing a major quest uses 10%, side quests use 5%, other random achievements use 2.5%. Since I work these amounts out when they level, I have the numbers right there which makes it easy to track.Yeah, I can't be bothered with XP as a DM. If I award XP for killing monsters, I feel like I need to award points for other achievements, which means I have to come up with XP for different achievements - which means I will also have to come up with XP rewards on the fly, or sit down after each session and work it out. I've got enough on my plate as a DM, so no thanks.
Also, since I track the xp for the whole party (as in I have a single xp total rather than tracking for each individual) it keeps people at the same level. I could just use milestone levelling, but people like knowing they have an xp track and seeing how close they are to the next level.