I've got problems with Lotus Notes, too. Notes is what we use at work, currently. In general it works okay, but iCalendar support is spotty or odd in some ways. You can't click on and open an iCalendar file on the web for example (in Notes 6 anyway, we're not using 6.5 yet); you have to drag it to your in-basket. From there, it's like a meeting invitation, you have to open it in your in-box, then perform another action to add it to your calendar. This of course makes adding events from someone else's site to your calendar a pain. It's not as much of a pain as Palm's non-support of iCalendar, but a pain none the less. I've heard it will be fixed in 6.5 or 7.0, but I have no confirmation of that.