If you are not an iBoy, I must say you will love N9 if you were given both the N9 and iPhone (4 or 4S).
In simple and straight comment, iPhone 4 will lead N9 only with the help of wide range of Apps and Games available... if not considering Apps more than anything then (IMO) N9 competes any other phone with all its hardware and software (while yet to have updates)
With N9, you will get most of the things out-of-the-box. no restriction, fully open to root, social apps are fully integrated with the OS, Gtalk fully integrated, Skype fully integrated, Messaging/Chat fully integrated.
There are only games which you get out-of-the-box with N9 those are NFS shift HD, AngryBirds, Golf HD, and Galaxy on Fire HD.. No such games are available additionally for MeeGo yet (or don't know if they will be) but the development I've seen after the launch is appreciable.
Lumia 800, however, will have up-hand of Apps as well. I'll go for Lumia ONLY FOR its design and that's the most attractive part of N9 as well. But N9 still beats all in uniqueness and easiness of User Interface (amongst all).. N9 super passes Lumia in most of the hardware aspects, though Lumia has more Processor Clock Speed.
Well 3500 updates are yet to come via Software Update to N9.
But let me tell you again.. the Apps limitation on N9 is really a fact to be considered if you want Apps and Games more than anything then N9 is not for you. However there are still many useful Apps for N9 e.g. CuteTube for youtube download, DropN9 for dropbox, File Managers, Third party Twitter and Facebook clients in addition to stock ones. Official Sports Tracker, Paid Professional Camera apps,
a few at recently launched website http://n9-apps.com/
you can explore Nokia Store by selecting N9 as your preferred device.