New things introduced in gen V? Wild double battles. Cheryl, I don't what you're talking about. Okay yeah I forgot the stat trainers from D/P/Pt, I was thinking more that this is the first time you can consistantly have wild double battles, and use two of your own pokemon.
Also the grass in areas will randomly shake, usually denoting the presence of tabunne, or occasionally some other rare pokemon.
Tabunne gives out more exp than chansey a hell of a lot of exp, and has like, no practical attacking power a tendency to spam non damaging moves, so it's brilliant for speedy levelling.