I know i've been spamming it up recently, but I'd just like to add some weight to this (however small).
Recently I've been doing some 'preliminary' metta, before moving onto anapanasati, really focusing on moving that metta outwards, towards specific people and then out to the world in general, one can't help but smile, it definately brings a little pīti out to play, and it makes focus so much easier. For me it's been the like the difference of filling the car up with 91 unleaded, and filling it up with 98 super premium octane.
Hope you all have a Mettaful day.
Jack

"But, Udāyi, let be the past, let be the future, I shall set you forth the Teaching: When there is this this is, with arising of this this arises; when there is not this this is not, with cessation of this this ceases." - Majjhima ii,32
Nanavira Thera's teachings - An existential approach to the Dhamma:
http://bit.ly/LDsGHg