I think this was mentioned before but I wanted to make sure it's visible for any discussion.
Right now, conversion of leads from the inbox automatically starts a deal. While functional for some, this is really dependent on your own definition of a deal. Depending on someone's business and sales process, some will start deals early. Other sales teams will apply certain criteria that need to be met before an actual deal is started. We're in the 2nd group.
So for this purpose, it would be tremendously useful to allow creation of deal creation on lead conversion as an option. Suspects (unqualified - leads) can become (qualified) prospects without deals.
Again, this is somewhat different for many and dependent on how someone has organized their sales process. To capture the broadest use case, I would like to recommend making this optional.
FYI - @Mike van der Valk