In my Heroes By Trade tests I got some feedback that the races in my particular fantasy world weren't compelling enough numerically. At level 1 they were reasonably differentiated but as time went by many of the differences between the races vanished because they could be replicated simply by buying particular Skills or Powers. Initially many of the races were set apart by having a short list of Skills they had to choose from - as an example, Trolls need to choose two of Intimidate, Stealth, Camouflage, and Wilderness to be trained in to start the game. I came up with an idea to keep races differentiated over time that I adapted/stole from 4th edition DnD, which is to let people buy racial abilities as they level up.
All characters of a particular race will still get baseline abilities like the Troll getting Thick Hide which grants them +1 Armour and +1 Resist. However, as they level up they will have the option of buying new abilities that are unique to their race. Humans can purchase an increase to the number of Fate Points they receive, Gnomes can tumble through squares occupied by large creatures, and Sylphs will be able to upgrade their wings to have more powerful flight. Every race will have a number of cool things that they *can* do but which not everyone who takes that race will be able to do. Hopefully this will make racial choices continue to be relevant and interesting as characters get more powerful and also let people of the same race differentiate themselves if they choose to.
I feel like in DnD this style didn't work well partly because the feats were terribly balanced but mostly because of organization - all the racial abilities were listed under feats and as such were difficult to find if you were looking for them and hard to avoid if you didn't want them. It seems like a small thing but I think those feats would have gone over a lot better if they could have been neatly placed under race instead of just randomly scattered throughout the feat lists - I certainly would have liked to know what cool stuff a dwarf could learn to do when reading the other details about dwarves.
This all ties in with a philosophy of mine about gaming systems. That is, the system is not necessary to do cool things and have fun but people feel much more immersed in the game when the system supports their intuitive understanding of how things should work. I think people want characters to be able to have unique abilities and they want a character's race to matter in terms of what amazing abilities they can manifest.