After 3 years of using some variation of Palm OS smartphone and Palm Desktop, I've switched over to using the Treo Pro (Windows Mobile) and Celio Redfly for mobile calendar and list management, and Outlook on the desktop at work. I always do my weekly reviews off site to avoid getting sucked into the busy trap at work, so using the Redfly as an external screen and keyboard for the Treo allows me to avoid one more layer of synchronization issues, and I can choose any venue without having to worry about power outlets or wireless connections.
Moving to POS to WM wasn't easy, especially due to complications with ActiveSync. But with no further POS products in the pipeline, WM at least offers a wider array of smartphone form factors and specs to choose from. I tried to Palm Pre for a week and quickly realized it wasn't for me. I prefer the efficiency of front-facing keyboards to sliders, and the lack of categorized tasks was unacceptible. Synergy in its current state isn't anywhere near a robust as local syncing alternatives.
For basic PIM, I'm just using the built-in apps: Tasks, Calendar and Notes. But I'm considering adding Checklist Pro and Pocket Mindmap to augment my project planning.