I get many calls from customers thinking we can just pig tail copper onto aluminum with the proper # 63 marrette. I have always thought it was best to replace the devices with c0/alr devices but i havent seen these in Decora.

I dont think there is such an animal as a CO/ALR rated decora device..
A.D

Yes I have some on order through Westburn Ruddy, they are purple, chemically treated and allow for different expansion rates or so the sales promo tells me. I thought the was a marrett with a copper tail that was allowed for AL wired homes. I have seen a few homes with AL/CU mixed and was looking for the best way (penetrox and an 833 with a piece of CU takes up space)to help these people out.

Sorry, I should have read the question better and I have not seen a AL Decora device.

Has anyone seen a Cu/AL pigtail (well-twisted and w/compound) go bad?

I'm curious because to me it seems like as good - or better - a connection than #12 AL wrapped on the screw terminal. Then you don't need to keep AL-rated devices in the truck.

I haven't seen many cu/al connections, at all. Has anyone seen a cu/al connection last for 10 or 20 years?

Please correct me but isn't that the problem: 10-20 years of mixed metals causing corrosion and heat? I understand that Penetrox should be redone every 5 years (but they say the fixture should be replaced every 5 years)

what about split bolts?

I know the OP and most of the other posters in this thread are from the great white north, but wanted to chime in anyway.
Last year I switched to the connectors below after learning some unsavory info about those purple wirenuts.
These are listed for CU and AL wires. The only thing is that you will need to buy and use a torque-limiting screwdriver to install them for UL/CSA listing compliance. They can also fill up a device box quickly if you have several splices to make.
The company sent a free sample connector before I purchased in quantity.

Here is the product link. http://www.alcopstore.com/

I got the sample also but i have not found a Canadian supplier for them yet

I have a stock of these i use for now.

http://www.tnb-canada.com/en/catalogues/online/comresconstruction/pdf/c5/09_marrcat_e.pdf

Doug,
I ordered them right from the Alcopstore website. I saw this on their Q&A webpage about shipping to Canada. No doubt you would get hammered on the freight charges though.

2) Do you ship to Canada?
Yes, we do. But, we need you to call us at 877-614-7185 so we can get you a custom shipping quote. We apologize in advance for any inconvenience.

I've used both methods of aluminum terminations (pigtails/COALR devices) COALR Devices are quick to use, however still not offered in DECORA. 63's (brown) are the maurettes I would use for CU/AL pigtailing. I have not heard of any problems with these methods. When performing this work at a house with aluminum wiring, usually I find evidence of burning/arcing in one or two splices.

I also use the brown #63/65's.
I was under the impression that you only need penatrox on STRANDED aluminum conductors (12-118[2]). I only use CO/ALR devices when there is a box fill problem. They're too expensive!!

Marette makes approved copper to Aluminum wire nuts and they are available at most Canadian Wholesale outlets.
Wire nuts compensate for the different expansion rates or copper, steel and aluminum. CU/AL approved devices are good but with the added expense IE a receptacle can be more than $12.00 that we see mostly copper tails and yes I know of them in use for more than 10 years.
The original problem with aluminum wire was related to the change from true brass screws to steel screws with brass or chrome plating. The aluminum expanded faster than the steel and would flow out from under the steel screw. This made the connection loose and we all know how that works out. We don't see Loomex (Romex) in aluminum except for range wire and feeders. The wire itself has changed too. Most have had alloys added to improve the mechanical properties and to help with the expansion problems. A range plug is usually approved for both CU and AL.
From personal experience I go with pig tails over devices for the normal 15 amp branch circuits. So far no call backs where the right connector was used.

Does the #63 or #65 marrette wire connector need the anti oxidant There is nothing on the box stating it has to be used. just says cu-cu cu-AL AL-AL

In Canada all aluminium connections require an anti oxidizing compound for stranded wires. See 12-118 for all the rules covering the termination of aluminium wires. some terminations and splices are approved without it.
The rules don't otherwise define a requirement for anti-oxidant pig tail connections of solid aluminium to solid or stranded copper. Bottom line is follow the instruction the box if you are not installing a copper tail to stranded aluminium wire.