In fact, that's one of my only complaints with eM Client 4 (free for personal use, $49.95 for Pro), which runs EssentialPIM a very close second. It makes simple work of importing data from Outlook (among other sources), though it doesn't actually sync with the program. And it suffers from that irksome reply/forward problem.
Even so, eM Client is arguably the most modern and compelling Outlook alternative available today. It's particularly good at integrating with Webmail services like Gmail, Hotmail, and Yahoo, and it supports multiple calendars (both local and cloud). It also supports instant messaging via services like Facebook and GTalk, and the clever Sidebar pulls contact details from Facebook when available.
Perhaps best of all, it offers contact, calendar, and task sync with Android, BlackBerry, iOS, and Windows Mobile devices, though this comes courtesy of the optional Sync2eM service. (The developer offers a free 60-day trial; I couldn't find any information on pricing after that.)
On the other hand, are desktop-based PIMs/mail managers even necessary anymore? There's a strong argument to be made for keeping all your data in your phone and synced to the cloud, without the hassles of desktop software. Obviously there's no one-size-fits-all solution, but I'm curious to hear which one works best for your situation.