Hi Patrick,
g_form.getReference just ends up calling the client-side GlideRecord API. In my opinion, client-side GlideRecord should be avoided as much as possible, since it usually results in a lot of data being transferred needlessly. If you are going to use it, use a callback (g_form.getReference accepts a callback as the second parameter). Client-side GlideRecord can also take a callback (passed in to the query method).
If you are going to use client-side GlideRecord (either through getReference, or directly), do so with a callback so it's non-blocking. However, you rarely need to get the entire record back when doing lookups, so a GlideAjax script which can return only the necessary information is typically a better choice.
Thanks
Cory
