Omniture is rather expensive and somewhat difficult to use. Scalability won't be a problem with either. A more fundamental decision point is understanding what

Omniture is rather expensive and somewhat difficult to use. Scalability won't be a problem with either. A more fundamental decision point is understanding what kinds of information you want to track:what metrics are important to you? You're at much greater risk of having an analytics package that doesn't help you answer meaningful questions in an actionable way than having one that won't scale. Google "pirate metrics for startups" for a little more insight. Also, you may want to explore one of the several "alternative" metrics packages, those that are better turned to funnel analysis or whatnot than either GA or Omniture seem to be.