Guardians: In a word, reflective. This would go well accompanying the main menu of a Marathon remake, with a slowly panning outer space scene in the background. I didn't like the synth pad as much as the more acoustic instruments.
Leela: The reverb is good for a standalone listening, but might seem weird if used in a Marathon level. The guitar certainly takes it in a fresh direction. I liked the asymmetric use of the right and left channels.
Swirls: So sad! A very full sound. Makes me think of running through Borderlands for some reason. It seems to almost lead off into some female vocals, which would seem appropriate for the Leela track. Not sure what you're going for at the end, but it does evoke a techy, 'cyberspace' feel.
Lastly, the style of your avatar is familiar. Where is it from?