I just posted a long reply to someone's forum question but think it's worth addressing as a new thread...
I wrote a very long article on the lack of support between iPhone and Lotus Notes/Domino, which is going to be published next week. I am very disappointed by IBM's entire mobile strategy and Lotus Domino/Notes is the worst offender. The whole raison d'etre of Notes is to provide document management and workflow - of which email is just one component - and mobile is CLEARLY the most ubiquitous, most pervasive and most convenient way to share documents and workflow processes with people inside and outside your organisation. Why they have ignore the iPhone/iPad platform completely escapes me. It has to rank up there with other incredible strategic blunders like when IBM let Bill Gates keep the MS-DOS OS for himself. What in the world is Lotus thinking??
Anyway, my rant is over...
I, too, have tried to sync Notes and iPhone/iPad. I don't have a solution for iPad - other than to do what another person in this forum suggested and access it through your Safari browser. On the iPhone, I would suggest the Exchange connector with the Notes Traveller on Domino. This syncs most things but not notebooks. It's also buggy.
Even better, my preference would be to use the middleware from CommonTime (they are based here in the UK, where I am writing this). They've been in this business over 10+ years and they run server-side software that mediates between your Lotus Domino Servers and your iPhone/iPad devices (as well as Blackberry, Nokia, etc). It will sync most of the data you need with a few exceptions (there's that notebook issue again). I have been a happy customer of CommonTime for over 8 years. I just wish that their custom design tools were easier to operate. This is useful when you want to have a custom Domino database made available to your iPhone/iPad. I have a bunch of custom-db-applications that I'd love to have replicate onto my iPad but the designing and programming is mind-bogglingly feature-rich and complicated. In the end, I subcontracted another firm to do the work for me.
One especially nice feature of CommonTime is the ability to combine the data from several server-side contacts db's into the one contacts app on the iPhone. However, two-way replication is a bit tricky in this scenario, as you have to write scripts to determine where contacts created on the iPhone/iPad should be written back to.
If you don't want to run middle-ware, then I would suggest using Google as the intermediary. I have successfully used Google to sync my iPhone back to Domino. Google supports iCal and the Mac Contacts as well, so that your Notes calendar and contacts information will appear in Google and in iCal on your Mac desktop, as well as on your iPhone. In some ways, this might be the best scenario if it remains future-proof. Google seems to be a pretty open player in this regard.
For some (obvious) reason, Google isn't the most forward in promoting how to integrate the iPhone/iPad with itself and then with Domino. There are people out there who have published instructions for this, so I suggest you do a search first and research it. I remember that it took a bit of settings finesses to not have to use iTunes as the sync intermediary with some of the data... Google does support the Exchange connector, which is how it's able to sync over-the-air to your iPhone/iPad device.