Rewards have, more often than not, been things that make your character better. You complete a quest and you get a new piece of equipment, or access to a new area, or even just a nice handful of experience toward the next level. But we've recently talked a bit about how leveling, and progression by extension, can get rather tedious. Spinksville also talked about this, discussing the differences between player rewards and character rewards, with the former being general rewards that stick with the player and aren't contingent upon or related to power level.
An excellent example is that of Klingons in Star Trek Online. The race has been a staple of the series ever since it began, and the Klingon Empire is one of the major political factions in the game... but it's not initially accessible to players. You have to complete a mission or reach Level 6 in order to unlock the option of playing a Klingon. Similarly, World of Warcraft gates its first hero class, the Death Knight, by requiring a level 55 character before one can be created.
Player rewards contribue less to a sense of avatar progress, but they also help keep the power level slightly lower, as well as providing benefits that you can take with you, so to speak. On the other hand, they're vulnerable to feeling less like rewards because they're unrelated to the character who obtained them. We've all been well-versed in the endgame grind for gear acquisition, however, so the post's call for more player rewards might be a welcome change for many of us.