Depends on what you're trying to do. Canna A+B runs a calcium/nitrogen dominant system that does a fantastic job vegetating plants and growing mothers. I might recommend a silicon product and something with chelated iron in it (especially if using filtered water) but other than that you're good to go.
There are a vast array of supplements to choose from should you want to assist any of the many plant processes. Vitamins and hormones and a never ending number of PK ratios and micro-element supplements. Most people find themselves adding some of these to the Canna system at one time or another.
My opinion on it is that you could do better if you're selecting a bloom formula and you're trying to keep things simple and inexpensive. Grow-Micro-Bloom systems will offer you versatility when working through the growth stages. Many companies offer these kinds of systems.
Botanicare CNS 17 Coco/Soil Grow, Bloom, and Ripe is another inexpensive alternative and it is packaged as a "one-part" system.
As a coco grower who has used Canna and has decided to stop using it the best alternatives are a three-part GMB system (can be just Micro/Bloom) or a one-part coco specific system like CNS 17. If Canna costs about $25 for 1L of A and 1L of B then you can get a gallon of CNS 17 Ripe for less than that (or a quart of each) or you can spend maybe $5 more and get a quart of Micro and a gallon of Bloom from a 3-part system.
Canna locks you into their ratio, and at the end of the day I think you'll find it to be short on Potassium and lacking crucial late flowering Calcium to Magnesium ratio changes. If you can find a way to supplement this BEFORE it's a problem you can do quite well in Canna. It is important to include at least Cannazym if you want to stick with their system for the 0-2-1 PK boost that it will bring. You can dial in your PK levels a little bit against the A+B system and this makes a huge difference to flower initiation and production.
To each their own.
