Per se it is not complicated - if the service or software you want to sync with supports the open SyncML standard, setup is simple - the provider will give you a URL, a login, and the names of the datatypes supported (like "contacts", "events" etc.). You enter these in the settings, and sync works.
Unfortunately, large and successful service providers are often not too inclined to support existing standards like SyncML - they prefer defining their own and rely on developers creating sync apps directly targeted at their offering, or provide these themselves. And because they are large and strong in the market, for all large services you'll find an app directly syncing with the service.
We make it clear in the app description at AppStore that our software entirely relies on SyncML, and does not directly support any particular service to avoid you to buy the product with the wrong expectations.
Todo+Cal+Sync comes with one of the best SyncML clients (and since version 2.0, also a mobile server) you can get. If your calendaring, contact or todo service does support SyncML, it will work fine, and while setup is a bit more than pressing a button, it is not really complicated at all.
If the service you want to sync with does not support SyncML, you need a solution bridging the gap. Like GooSync for Google Calendar, or Winfonie for window desktop based calendars. Of course, an additional service or tool makes setup more complex, and also costs extra money.
We rely on SyncML because we think that sync should be vendor-independent, and interoperable. If your preferred service or software does not support SyncML, please let the providers know that you are looking for it. | 
