What are the locations of all the purchasable houses in Skyrim

The PC will support mods:

Bethesda's fifth Elder Scrolls game, like Oblivion before it, will allow for extensive player customization, according to the developer. "We've always been impressed with what the community has done with our tools," a rep for the company said on its forums, revealing, "Like the Elder Scrolls Construction Set for Morrowind and Oblivion, we plan to release [a] Creation Kit so you guys can mod Skyrim."

The immediate predecessor, Oblivion, has seen countless mods -- everything from new characters to online play. We can only imagine what the Skyrim community will manage to create while we wait for Bethesda to finish the most ambitious Skyrim mod, Fallout 4.

Source: Joystiq

The PC also supports console commands which can be convenient if there is a bug with quest items.

The Xbox 360 has the first 2 DLCs exclusively for 30 days.

Source: Gamespot

As far as I've found all three versions support achievements/trophies.

When you join a "college" or a "group" like Winterhold Academy or company in Windhelm, they give you a "dorm" room.

When you notice that some room might be yours open the console (tilde key) click on wardrobe to select it and type IsOwner and you should see who it belongs to exactly. If it is you, then it is a safe place to store your items.

Also to make sure you can put item in container and go away for 48h that is the time items know to disappear.

Note:aiming at bed and seeing if it is red or not is easy and quick way,but it is not the most accurate since you can sleep in some beds even if you don't own the cabinets...