My opinion would be to start out fairly simple, so that you can concentrate on the content. You can always switch themes at a later date, which is the great thing about wordpress.

See, you can always pick a more complex theme now and tinker around with it, but then later on you decide it does not suit your tastes so all that time spent tinkering has been wasted (except for the learning aspect of it).

I guess it comes down to if you've already decided on a more complex theme and you plan to stick with it. I'm assuming, however, you may still be in the development phase. So if that's the case, start out simple, create your content and as your site grows you will know what direction you want to go in which will help you better decide on what 'complexities' you would actually want in a theme.