I can't care about maemo features if those are integrated in a device that has little meaning for the enterprise.
It is not only about Open Source. It is about Linux based Open Source. N97 is not going to run Firefox or OpenOffice or Phyton or apache+php or a printer device or a miriad of different software on it, because there are no Symbian based servers, no Symbian based Desktops and no Symbian based old computers with people making Links run on them with javascript enabled.
But nokia has no equivalent in their potfolio so if N900 acts as a phone, then it is better to carry around a big phone-tablet that a big phone and a tablet.