Sync'Em is designed to be a sync hub and has an extensive collection of features:

• highly flexible underlying software architecture
• multiple sync setups — create as many syncing configurations as required
• multiple information sources per sync setup — sync multiple information sources (e.g., an Exchange account, a Google/Gmail account and your Mac)
• sync any supported information sources — e.g., sync Exchange accounts with other Exchange accounts and/or Google accounts, even without syncing to your Mac's iCal/Address Book
• can support polled update and/or push update models per information source
• extensive flexibility and configurability
• sync any number of same-kind information sources with each other
• support for more than just standard configurations (e.g., an Exchange account's Home and Work calendar folders can be configured as unique information sources and participate in different sync setups)
• sync unidirectionally (either "to" or "from") or bidirectionally for each information source
• set different sync intervals for each information source
• set different schedules for each information source
• set different filters for each information source
• sophisticated but easy-to-use conflict resolution
• easy n-way conflict resolution (i.e., when the same item has been changed in multiple information sources within a sync interval)
• deferred conflict resolution allowed — still syncs all other items but lets you deal with conflict resolution later
• uses proprietary technology for the Sync'Em Sync Engine, not OS X's Sync Services
• allows for n-way parallel sync operations with increased performance, including via "push" technology
• underlying engine can support almost any kind of information sources
• increased capability to handle non-Apple information sources
• enables non-Apple to non-Apple syncing — e.g., back up your Exchange contacts and calendar "directly" to Google
• however, the Sync'Em Sync Engine must access iCal and Address Book via Sync Services
• Sync'Em stores and retrieves changes to iCal and Address Book information sources via OS X's Sync Services — but the Sync'Em Sync Engine determines what needs to be sync'd and performs conflict resolution
• Sync'Em-sync'd iCal and Address Book information is available to any sync application that uses OS X's Sync Services — i.e., iSync, iTunes, etc.
• if you can't get something sync'd directly to your iPhone, you can sync to your Mac then to your iPhone via iTunes (e.g., if your Exchange server doesn't support your iPhone)
• syncing can occur without a User being logged in
• the exceptions are Apple Address Book and iCal because they must be accessed via OS X's Sync Services and Sync Services are only User-space accessible (i.e., only available via a logged-in User)
• helps avoid many of the Sync Services problems, including information loss
• syncing is via direct connection
• allows tightly controlled group sharing of information sources
• no external server is involved (such as with Plaxo or MobileMe)
• helps protect personal and proprietary information
• helps increase security
• employs an ultra-friendly error-reporting model
• Sync'Em menu extra provides real-time status indication and control
• errors are cached to minimize workflow interruptions
• preferences customize error-reporting behavior