Of course, those things are not guaranteeing delivery, but they play an important role.
I just recently had an issue where I tried to send an email to a someone I'd just met. The cc-part that went to my gmail-account got through fine. He didn't even receive spam. After I set up spf, I successfully sent an email to the exact same gmail address.
If gmail had rejected the mail, there'd be no problem -- then I'd know that I'd have to take action. Quietly eating the mail... not cool.
I wonder how long until the only way to send email into gmail/outlook is to set up routing rules that send email to gmail/outlook addresses by logging in to those respective services, and sending directly, bypassing traditional unauthenticated smtp... presumably setting up one "major" delivery would be enough, as gmail can't ignore outlook.com and vice-versa...
If you have the same clean ips from pre dkim/domainkeys days then don't lose them, or it may be an uphill battle which I would be surprised if you didn't engage dkim to aid in fighting at that point.