Is an xla still rqd to call the COM add-in?

I am (still) considering my options wrt converting my vba xl add-in to
a COM add-in (c/- Office Developer). As I have never actually seen a
COM add-in I am curious to know how this would work. For example, do I
still need an xla module to add my commandbar to xl and then call the
subs/functions in the COM add-in or can I directly compile the entire
xla as it is?

Thanks a lot,
Andrew