Yes, ultimately it matters whether Morpheus users share files now that it has become a Gnutella client. This fact, however, is not directly connected to how Morpheus performs as an ultrapeer now that it's here. Non-sharing users are also connecting to LW ultrapeers and contribute to the degradation of the network generally. Yet even with this state of affairs, LW performs better as an ultrapeer than Morpheus.
BTW, if hardly anyone shared on the old Morpheus network, what on earth was the incentive for the people who did?