Thumpango, can I go against the tide of opinion here and say my first solo was a bit of a disappointment.
Don't get me wrong, I really enjoyed it in hindsight, but it was over before I knew it had happened and left me feeling a bit empty. I did walk round with the proverbial BIG GRIN for several days, so it must have been good, but just not the highpoint of my entire life as it is for some.
I was actually dreading it in an odd sort of way. I put off getting my medical for a couple of weeks so I could go flying safe in the knowledge that my instructor wasn't going to desert me. I (almost) hoped I'd fail my airlaw because I knew that I'd probably have to solo that afternoon if I passed. When it finally happened the conversation went like this:
Instructor: "OK, make this one a full stop and do one on your own"
Me: "Err... but the weather isn't perfect"
Instructor: "It's fine"
Me: "But, I'm a bit tired"
Instructor: "You've been fine so far"
Me: "But I only just passed the air law, what if I forget somthing"
etc. etc.
Get the picture?
Anyway, I think it might have been this irrational fear that spoilt it a bit for me, so I suppose my point is, whether your scared to do it, or can't wait and are frustrated, relax and don't worry and you'll get the most out of it. Also, the instructor will know when you're ready even if you don't.
I found that my first real circuit-bashing session was much more satisfying than the first solo - a whole hour completley on my own. That's when I first felt like a pilot.
Someone on here once said that when you get sent solo, you're being payed the biggest compliment of your life. That I DO agree with, so don't rush into it, and don't worry, it'll happen when it's meant to.