I've now been using the iPhone 4 for a few weeks, and in a lot of ways it is a huge improvement on the 3GS. The screen is much better, the camera is much better, I prefer the squarer shape and the limited multi-tasking is welcome.
However, apart from the well-publicised issues with the signal quality and the other items which really annoy me such as the limited multi-tasking, the fact that you have to use iTunes to activate and use it (without jailbreaking it, it is a work phone), the one thing which still makes the iPhone an expensive toy rather than a really useful tool is the lack of OpenVPN support.
I know that some of this functionality can be achieved by Jailbreaking and using other apps, but remember that this is a phone I don't own and can't mess with. If there was some way a kernel extension could be provided to allow tun/tap tunnelling to be used, then OpenVPN functionality would be possible, and this phone would suddenly become a lot more useful, allowing me to access the whole range of servers which are on different nodes of the VPN network I've developed for work. It would allow me to not worry about carting my laptop everywhere, just in case I need to access a remote server, and it would make my monitoring of system services so much easier.
It would seem however that this is a pipe (or tunnel) dream as this extra functionality is not likely to be added to the iOS by Apple.
So, unfortunately, while I have tried very hard to love the iPhone, and the iPhone 4 is much better than it's predecessors, I still cannot bring myself to recommend it to anybody who wants to use it for serious sysadmin tasks. I would now love to get my hands on a HTC Desire with the Froyo version of Android on it. From talking to people who have used it, it has the potential to be a real iPhone-killer for the average user, and Apple fan-boys can never be truly cured anyway.........