3.1 has brought a multitude of new content and in-game changes which you can undoubtedly tell by the myriad of bugs, the overloaded Blizzard support lines and the somewhat random looking realm crashes.
Still all in all I'd say the 3.1 patch went in rather smoothly considering its massive size... on the bright side the 20 minute patch download on my machine gave me ample time to take a closer look at the patch notes for 3.1 and there's a lot of interesting stuff in there.
I am sure you already encountered or read about your particular class' changes (I know I read the warlock changes first) so today we devote our post to the topic of changes that have been implemented for the convenience of players that no one ever seems to notice until you accidentally run into them:
1. Your land mounts mysteriously learned to swim, mind you not all of them do it very elegantly.
2. You can dual spec at level 40 for a 'mere' 1000 gold.
4. You can turn an option on in the interface menu that allows you to allocate talent points in your talent screen without actually allocating them until you press save (or learn rather)... that way you can change your spec multiple times until you're happy with it and then save it... This option is NOT turned on by default...
5. Bored? turn on the color blind mode in the options menu.
6. Try pressing 'ALT' while hovering over an item...
7. Turn on all the quest objective tracking options in the interface menu and even useable quest items will display in the objectives screen. Very handy if you don't have quest helper.
8. Your hearth timer got cut down to 30 minutes... no you really haven't been playing that long yet.
9. Horde mount vendors got a few new mounts to show for. Go to ogrimmar, bloodhoof village and brill and get your 3 mounts if you're still looking for some.
10. If you hapen to be in the area of feralas and see sprite darters go give them a good whacking, slim changes are you will find yourself a sprite darter pet (something previously only available to the alliance)
There we have it... 10 more or less useful and interesting facts from the 3.1 patch notes.
As always after each significant patch it pays to just run through all your options menus and visit your various class and profession trainers to pick up on all those things that have been added with the patch.
There's a lot more in the patch notes that may be of interest to you and I could've easily made it 20 random facts... but then you might as well go out and read the actual patch notes.