How & What can I gain from playing Rapid Games? I already have been playing tournament chess for around 4 years

 More games = more fun if you like faster chess. I made a decent living while in university playing 5 minute blitz but now it is all I can do to play one move in that time!

Playing Blitz is a great way to improve your opening repitoire. By playing a great number of blitz games you will be able to gauge what openings your strong and weak at. I use blitz to improve my openings but thats probably it. I dunno, it should also sharpen your game but you dont want to get messy and play 'flashy' pointless moves in serious games. Save the flashy moves for blitz where you might get away with them. 

Thanks for the feedback

I have avoided playing rapid(blitz and lightning) games for the past few years because I was told that it spoils your game and develops bad habits. Now I'm thinking of moving to faster games. Any tips?