Ubercart

My timeline for a simple product-based drupal/ubercart site is mid-may, should i develop in 1.x and upgrade to 2.x when it's out of beta, or start in 2.x now, and update as it comes along?

The main client requirements is that this will be a site that can "grow" with them for the next 5 years at least, something that can be updated easily (security updates, pathes). Obviously D6 will receive most of the attention in the next 1-2 years until Drupal 7 comes out, but the big question is, is 2.x ready and how long will it take to reach production phase?

Thanks for any suggestions,
Lu