For years one of the tools I used a lot was Microsofts Live Mesh tool. This tool made syncing files across multiple computers absolute childs play. You just set up the folders on all the required machines and the software just kept everything in sync.
However a year or so ago, Microsoft decided in their infinite wisdom to replace it with SkyDrive. The problem is that although SkyDrive does a great job to a degree it has 2 major issues as far as I'm concerned. 1) The folders must all be located under one parent folder and 2) there is total storage size limit and an individual file size limit of 2GB. This was particularly an issue when wanting to sync ISO images or large movies.
Folder Location - Not a huge issue, but it means that all the folders I sync are under a master c:\skydrive folder, whereas Live Mesh allowed folders anywhere to be synced.
Size - Skydrive offers 7GB to new users or if you had used from before April 2012, 25GB. All folders must be synced up to the cloud, but with Mesh although you had 5GB of space, you didn't have to store all folders in the cloud as selective sync. This meant that you could for instance sync hundreds of GBs of data on a peer to peer basis; but you weren't restricted by the 5GB online limit because you didn't have to use that as a mandatory storage area.
Two new players have appeared in recent months BitTorrent Sync and AeroFS. Both of these work much the same as the old Live Mesh, but without any free online space. However, as I run a dedicated home server that's on 24/7, this isn't an issue as it effectively serves as an unlimited "cloud" for me. (God I hate that term Cloud...!). BitTorrent Sync is available at http://labs.bittorrent.com/experiments/sync.html and AeroFS at https://aerofs.com/.
The major difference between the two seems to be that AeroFS still currently requires you to have a root folder and then everything underneath is synced, but with BitTorrent Sync you have more control over folder locations. The downside to BitTorrent Sync is that for every folder synced, there is a shared "secret" that needs to be entered on every machine that needs access to that folder. If you want a simple life then this will soon become a bit of a pain; but it ensures only those who you want to have access can get access. These secrets can also be read only too, so you really can control your data.
Currently I'm playing with both, but I reckon BitTorrent Sync is edging it.