Ok, so I've decided to take the plunge and buy my first road bike. I've been riding a hybrid for commuting and some group rides (35 miles max so far). For years I've wanted to train for a ride the STP (Seattle to Portland - double century) and I've decided 2008 is it. So far I'm enamored with the Ruby Expert. I had a fitting today at a LBS and it looks like the 48 will work for me (surprise surprise - I'm just 5' nothing and am used to always buying the smallest and still feeling like it is too big). It felt great but the typical NW winter day (rain, rain, rain) didn't allow for a test ride so I only got to try it out on a trainer. So, I'm making my list and checking it twice - my questions to you more experienced:

I'm leaning towards the triple over the compact double - based on my experience and fitness level on the low end - anything else I should consider with this decision?
Any comparable bikes I should consider test riding?
I've never done a test ride before - what should I expect? what should I be sure to do?

Anything else I'm missing?

Thanks in advance.