I have always liked Kadee couplers.  I was sold on them in my HO days, and I am glad they are made for Large Scale.  They are the closest thing to a "standard" in our hobby, where we have every manufacturer making their own interpretation of a knuckle coupler, or imitating the hook 'n loop that LGB came out with many years ago. 
    When I started in this hobby, I had mostly Aristo rolling stock, and had considered standardizing on the Aristo knuckle for awhile, but decided against it for the following reasons; the car spacing was too large, car spotting was impossible away from an uncoupling track, the coupler does not work too well with other brands of knuckle couplers, and Aristo couplers do not mount easily on other brands of rolling stock.  I wanted a coupler that looked prototypically correct and would work well during my operating sessions, and the Kadee seemed to fit the bill.
    The Kadee large scale coupler is basically a larger version of Kadee's HO coupler, that has become the unofficial standard of HO railroaders across the country.  The Large Scale couplers come in two flavors, "G" scale and "#1" scale.  These are 1.22.5 and 1:32 scale respectively.  In Kadee lists, G scale couplers are listed as three digit numbers and the #1 scale coupler are listed as four digit numbers. 
    The pros and cons of using Kadee couplers and "G" verses "#1" are numerous;  The "G" couplers are large but stay coupled better in more abrupt terrain and less than perfect track than the #1 Scale couplers, Car spacing is larger with "G" than #1 Scale, but can be reduced with some work on draft gear, The "G" coupler will couple with LGB, Aristo, USA and Lionel knuckles, whereas the #1 does not do so well, and it doesn't work with Bachmann at all,  Both couplers work well on any part of your layout when it comes to coupling, Automatic uncoupling is easy and fairly reliable with intrack magnets. The magnets do get in the way of track cleaning and will trip sound system functions that you may not want.  Springs and trip pins will rust if cars are left out in the weather.  Proper coupler height is a MUST for reliable uncoupling and delayed uncoupling, which allows you to spot cars on a siding by pushing them into location.  Slow speed engine control is a MUST also for the uncoupling and delayed uncoupling function to work.  A tool that is helpful for manually uncoupling is a long 3/16" straight blade screw driver. Just place the blade in the gap between couplers and twist 90 degrees. The cars will pop apart very easily.  An inexpensive uncoupling tool can be made from a stick (orange stick, chop stick) with one side whittled flat similar to the blade of your screw driver.
    If you decide to go the Kadee route, you should purchase their coupler height gauge.  There are two versions of this tool with #829 being the #1 scale and #880 for the G scale couplers.   These couplers are very sensitive to mounting height in comparison to the standard manufacturers' knuckles.  Too high or to low will cause uncoupling, with the #1 scale being the most sensitive to height differences.  Couplers should be tested while under load to see if they perform correctly.  A load will pull the couplers down on cars where they are truck mounted. Tightening up the trucks for these truck mounted couplers, or adding shims will help alleviate this problem.  On locomotives like diesels, where the coupler is mounted on a pedestal, the pull will really move the coupler from its proper height.  A body shim may be required to prevent this action which could easily cause uncoupling. You may want to paint your couplers to look rusty, but be very careful. The mating surfaces must be free of all paint or they will not work properly. Make sure you do not get any paint in the mechanism or the couplers will not open and close as freely as they should.  Use Teflon powder lubricant on your couplers after painting, and you will improve their operation tremendously.  I have found that a product called Rustall, which mixes with alcohol, will minimize the sticking problem if you must have rusty looking couplers.
    It's your choice, if you are into operations and spotting and picking up cars, then Kadee couplers are for you. Kadee has a great web site which gives numerous coupler conversion articles for various brands of trains and specific installations.  They will promptly answer your e-mail and send diagrams to you if you have any questions or problems.  Should you lose some parts, call them or e-mail them, and they will replace them for free.

Kadee Conversion List:
Kadee Coupler Height Guage
Kadee #1 Scale Coupler on Left
Kadee G Scale Coupler on Right