Next Google update

I think I'm in the sandbox, do I have to wait for Google update to get out

[sherwood55]

This question has several parts: The background is I have a straightforward, easy to navigate, ecommerce site with about 450 pages based on some pretty competitive keywords. It has been up for almost 3 months.

I have some backlinks and some directory listings (just joined Yahoo), but none are seen by Google. I have a PR0 and I think I'm in the sandbox.

My site's pages have been cached by Google regularly and I get hits and high SERP for lesser keywords (much lesser!). This happens on Google searches where my PR is still 0.

I have optimized for keywords and am anxious that at some point Google will give me PR. Until that happens, I guess I won't rank for my main keywords, right? Is getting PR tied to a Google update...or just till they let me out of the sandbox? Any other advice would be very appreciated!