Anyone have any experience transmitting wirkess video at weddings.. I'm working with a DJ and would like to transmit my video signal to his plasmas..

To be honest, the compromises to quality are just too much to even bother with it.. for a decent setup, youre looking at LEAST 10k for the system..

it could work even with very cheap equipment (less than 100$).
there is of course some limitations. Emitter and receiver must not move.
They must fixed above heads (4 feet minimum) and antenna must be properly oriented. A good antenna on the receiver (6dB) is a must. high power is not required (100-250 mW is ok)
If you can , a high gain directional antenna is still better, pointed directly to the emitter. (wifi antenna)
I have done this several time and for sure you will not avoid some drop, but as long it is just to display on a screen, it dos not matter.
if you work on small distance, a coax wire is better and often simpler
the only advantage of wireless is when you have a room already full of people and need to establish a link very fast.

I transmit wireless videos at concerts not weddings but we have success with these units from Markertek.
http://www.markertek.com/Product.asp?baseItem=COP%2DPKG2&cat=VIDEOEQUIP&subcat=&prodClass=WRLESSV&mfg=&search=0&off=

We own 6 of them now. We feed the signals to either our Tricaster or VT4 depending on the number of cameras and back out to projectors and plasmas.

What Giroud said is important. We make certain that the antennas are high enough so there is clear line of sight.