Hi Savvyxeus,
You mentioned "40 of the users will be on-premise and the remaining will be remote users". Do you mean 40 user mailboxes will be on the local Exchange server and others will be moved to Office 365? If yes, you are not able to perform a cutover migration. You can only perform a Hybrid deployment. If I have misunderstood something, please let me know.
If all the mailboxes will be migrated to Office 365 at a time, you can use a Cutover migration. I understand you don't want to deploy SSO, but you need to run Dirsync. If so, you can skip step 3 in the article: http://community.office365.com/en-us/wikis/exchange/835.aspx
Moreover, no matter what migration you are using, hybrid or Cutover, it is recommended that you leave at least one Exchange 2010 Server for mailbox management since the users are synced from on-premises server to Office 365 via Dirsync.
Thanks,
Edward Qu