I was showing my game to some people and there was a 9 years old girl who demanded playing it so I decided to just go ahead and let her play until she got tired and see what would happen (not like it'd help me much since the game is practically finished anyway). Quick reminder, the game in question doesn't have any tutorial of any sort, it just throws you in straight into the first level (and hopes the level design makes up for it).
Skill: gonna be blunt, she didn't seem even remotely accustomed at platformers at all, at least traditional ones (maybe endless runners on mobile?), at the beginning she didn't even dare to move left (!?), and that lasted much longer than I could have ever expected. She improved rather quickly though, by the time she reached the first checkpoint she had a rather rough control of Sol (still reacting somewhat slowly, but obviously enough to get that far). By the end she had even figured out that crouching can help dodge some attacks, and that one of the power-ups is used to break some floors and allows access to some rooms with items.
Frustration: she didn't take very long to complain that it was very hard =P It still didn't stop her and she got to the first proper checkpoint some minutes later. I swear I keep getting this reaction from people, they complain like it was impossible then they make some serious progress some minutes later anyway (rather than just giving up). Having infinite lives probably helps though (but you still only respawn at checkpoints).
Controls: she figured out the basic controls in like a couple of seconds =P When she found a power-up the first thing she tried was press ? (this crouches), then press ? (this makes Sol looks up). She got it right in the third try (double jumping). Again, she didn't seem to even consider the possibility of other keys... like basically everybody else who tried the game except for one guy (quick conclusion: players won't bother trying more than beyond the original control set, at least unless you tell them otherwise)
Miscellaneous: when she found a breakable platform and she missed it (she overshot the jump and kept running after landing) she realized that the platform would most likely respawn and waited for it. Huh.
Also for posterity, when she left the computer the game was in this state:
That wait animation was so worth it XD
EDIT:
Addenum: girl took over the computer again and spent like a whole hour playing the game o.O; (and got to level four now, albeit not without cursing a lot at me first =P) I don't think I need to say more at this point...