Transmitters

Hi all,
hope your ready for another winter !! Do you need sleds for frosty takeoffs ?!!! lol

My question today:

I am looking at up grading my 72 mhz transmitterto digital, and was wondering what, if anything, I should be specificly looking for?
I quite like this one and will be the price range im looking at.

What would the 7th channel be used for?
Do I need it or is a 6 channel ok?
Wont be buying another controller for a while !!!

http://www.the436modelshop.co.nz/item_detail.asp?id=2730&category=104

http://www.rcnz.com/Shop/Service/Detail/Product/3152/Radio_Control_Sets/Futaba___7CAP_7ch_2_4G_Radio_Set.html (for specs, 436 Shop has it for $491)

Who and what do you all have and recommend ? (Not over the top prices)


Cheers :-)