It doesn't look like any gunners have taken a crack at this thread yet... I'll say something on behalf of my AD brethren, but bear in mind that I'm just a mudgunner and haven't had any AD training.
Canada's air defence artillery is pretty good overall. Compared to the field side, which is still using 60's era platforms like the M109 and older guns like the C3, the air defence kit we have is modern (developed in the 80's). The ADATS is an outstanding piece of kit, as it can engage both aerial and armoured ground targets, and has a good radar system.
As well as the ADATS, the AD uses Javelin manportable missiles and 35mm guns linked to Skyguard radars. However, these systems are likely to be dropped soon in favour of a primary focus on ADATS (Javelin may be kept in a residual capacity). ADATS will be re-engineered and placed on a LAV chassis (that's the plan) and the Army wants to mix it with TOW and the MGS to make an anti-tank organization. What effect this may have on air defence training remains to be seen, but that capability will still exist.
Compared to the States... Well, the Javeling is a VERY Short Range system, while ADATS is a Short range system. Canada possesses no long range system like the US Patriot; but, on the other hand, the US doesn't really have a ground-based air defence system to cover the gap between their Stingers and their Patriot. Our ADATS fills that gap rather nicely, as I understand.... It's one of those few things that we have and they don't.
Now, manning is a big problem - like the rest of the army; lack of funds for training (live missiles are VERY expensive) and the uncertainty about the future resulting from the new anti-tank role are making life hard for the air defenders. Also, there aren't a lot of platforms - Canada only bought 36 ADATS systems, and only has one Reg Force regiment (4th Air Defence Regiment) composed of two batteries.
So in short, the equipment's good, but there's not a lot of it and the pressure on the organization is very high right now.
If there's any birdgunners in the forum who know more than I do, please add your thoughts....