Read Act 2, Scene 5, lines 1-17. Are these lines an example of a soliloquy or an aside? What do they reveal about Juliet?

These lines fit better into the definition of a soliloquy.  

Asides are usually short utterances (often one, two, or three lines long), which a character mutters to himself or to the audience while there are other characters onstage.  The aside is not heard by the other characters.   Asides interrupt the action for just a moment so a character can deliver his or her reaction or opinion.

Soliloquies, on the other hand, are longer...

These lines fit better into the definition of a soliloquy.  

Asides are usually short utterances (often one, two, or three lines long), which a character mutters to himself or to the audience while there are other characters onstage.  The aside is not heard by the other characters.   Asides interrupt the action for just a moment so a character can deliver his or her reaction or opinion.

Soliloquies, on the other hand, are longer speeches usually given when the character is alone.  They give a more in-depth glimpse into the character's thoughts.  Soliloquies move the action along by showing us a character's inner struggle, creating tension, and/or setting up his or her motivation for something they are about to do. 

The main message we get from this soliloquy is that Juliet is on tetherhooks while waiting for her nurse to come back with a message from Romeo.  Juliet tells us how she is feeling: the nurse promised, at 9 o'clock, to return in half an hour.  It is now 12.  The time has passed slowly.  Juliet is frustrated with the nurse's slowness ("O she is lame!").   This gives us a sense of Juliet's tension and makes it all the funnier when the nurse, once she returns, takes her sweet time in getting to the point.

Juliet realizes that she feels this way because she is in love.  "Love's heralds should be thoughts" because lovers are so impatient to get word from one another.  That is why, Juliet says, Cupid is shown with wings.  She is making a psychological observation about love based on her own experience.

Finally, Juliet is self-aware enough to realize that the nurse does not share her sense of urgency because the nurse is older, not a teenager in love.  

Had she affections and warm youthful blood,

She would be swift in motion as a ball.

...

But old folks -- many feign as they were dead,

Unwieldy, slow, heavy, and pale as lead.

In these four lines, Juliet goes from recognizing that the nurse does not feel as she does, to expressing the teenager's universal frustration with her stodgy elders. 

Thus, this speech shows us that Juliet is impatient, infatuated, self-aware, insightful, and frustrated.