DJCCguy -
I agree with the after 'there is a serious side to the flight' the remainder of the demo being silly-ness free. Frankly, I would rather the odd joke slipped in than a monotone drill sergeant voice, or worse yet, incessant giggling/laughter from a CS who finds something hillarious - especially when the rest of the cabin has no idea what it is. Granted it can be difficult/a pain when row one try their hardest to lure you into a joke or distract.
That said: Prior to 'serious side to the flight' I think it's an excellent way to gain the attention of passengers if done appropriately (which most of the time it is). Do a bit of a search on 'passive safety briefings' (whereby the attention is requested of pax, and the safety features are pointed out - like you would get if the CS just read the text word for word). The ATSB did a pretty big study in conjunction with Virgin Blue and a number of Australian/Asian airlines, and the results in evac trials using both active and passive safety briefings as well as the different commands used at different airlines - are quite interesting. It does make a difference.
On the business flights its not really appropriate - but if you have the right crowd - I don't see a problem with a little bit of light-heartedness.
We may do four flights a day, many of our passengers would be lucky to do two a year.
Finally, if there is one little gripe I have about safety demonstrations at any airline (and it happens at every airline), its those who don't demonstrate the oxygen mask and life jacket correctly:
The oxygen mask should be held close to your face and the strap be around the back of your head - not 1ft off your nose with the strap above your forehead. And dont yank it so hard that when it drops that in real life the pax will follow your lead and pull them out of the roof. Research following a number of depressurisations show that a number of people follow the demo exactly how its done - tried to use the things holding them like the crew do in the demo - if they hadnt already pulled it out of the socket. The life jacket waist strap should be pulled tight - not pulled an inch and left to dangle around the back of your knees - and dont yank those toggles, memory learning will put you and the pax at risk of doing it with your live one in the cabin prep demo (when you actually need it!).
(Not my imagination there - proper research has been done on it).