There has been an extensive discussion on the topic of Klyros full flight vs. gliding, in
this thread.
And yes, I think Klyros will initially replace the Enki at the top of the popularity contest. However, once there is more detail inplemented rule-wise, their specific disadvantages will be more pronounced, evening this out IMO (see end of this post for details).
I think there need to be skills for both flight and swimming. Not only that, but endurance and other physical properties need to be developed to become proficient in flight.
If you can breathe underwater, but can\'t swim, you\'ll have to walk, which is quite slow, even without considering the extra distance to the bottom and up again, and also disregarding the fact that lakes tend to be quite muddy and hard to walk through.
I agree with Gronomist on the agility issue. Wings will be extremely annoying when you\'re trying to move through the average medieval forest. PS won\'t have the extensive forests that were present in RL medieval times due to the relatively small size and large population of the stalactite compared to a RL planet, but there will still be some. And while walking, they would also be a bit of a drawback unless you can
1) fold them tightly around yourself or
2) flap them to propell you, making running way quicker, though only on terrain that allows for it.
Therefore, I think movement speeds would be quite extreme for Klyros in comparison to all other races: extremely fast on plains / wide roads, extremely slow in forests.
Summarising, Klyros disadvantages are:
No heavy armor
Fragility
Wingedness
This means:
Not top choice for fighting due to being easily damaged
Due to size and wingedness not top choice for rogues, either
Due to wingedness not good for hunting
Not top choice for mages, either, as there are races more gifted in it
This leaves them to be a reasonable choice for only a few border professions:
Fisher
Explorer
Artist