I don't like them, but I don't hate them either, they are what I would consider to be a baseline barrel.
More expensive barrels will perform a bit better than a CJ, as long as they aren't Airsoft Philosopher, but the gain you get from one is usually not as big as from stock to CJ.
In my journey through airsoft accuracy, I have found that internal surface finish is the most important thing, followed by crown, straightness, and a number of other things.
A junk barrel can be made great with some polishing or lapping, and can perform as well as an EdGi, but the reason you buy a more expensive barrel is to get one with a tighter bore and good surface finish, as stock barrels will have a larger bore usually, and lapping will increase that even more which will lower your power.
If you are set on a Maple Leaf you shouldn't be all that disappointed, but if you can, I would recommend that you buy an ESC Works 5.98 barrel, cheap 6.01 barrel and lap it following the guide in my signature, or buy a DaVinci and maybe lap it. EdGi, Lambda, and PDI are good but overpriced, and I wouldn't pay more than $50 for a plated barrel such as Action Army, Stalker Morpheus, or TNT.