<p>Our company is considering upgrading our SQL server. </p>

<p>At this point, would it be better to upgrade to 2005 or 2008?</p>

<p>Here are some of my considerations:</p>

<ul>
<li>Features</li>
<li>Licensing costs</li>
<li>Learning curve</li>
</ul>

<p>Bear in mind our staff has already been using SQL server 2000 for many years.</p>

2005 is already quite different from 2000, at least in best practices, as a number of things like error handling are greatly improved.  As far as learning curve is concerned, if you're going to throw the learning curveball at them anyway, they're probably better off learning the new technology rather than the one that is already a few years old.
Beyond that though, it's difficult to comment on new features without you providing any info on what kind of work your company does.  One thing I'm very excited about in SQL 2008 is the geospatial data type that I wish had come out a few months prior (perhaps, the initial planned release date) as they would have made our huge mapping application much easier...