i am a PPG certified painter with about 40 years of experience.
i have been spraying water base paint for about 6 years now.

in my opinion water base paint is actually easier to use than solvent born paint. it's also faster drying, has better durability and there are more consistent color matches with it. also. the paint it usually 30% or more cheaper than solvent. the top coats used with it are more $$$ so it evens out in the end.
the biggest problem with it is your facility must be set up for it to use it properly. you will need airflow enhancers and extremely dry compressed air to use it properly. you also can't use cheap spray guns when you paint it.you get the best results when using guns designed for water base paint.
my biggest complaint about it is dirt in the paint and correcting them. correcting dirt in the base coat is extremely difficult in the painting process compared to solvent paint. also the techniques required to spray it create dirt in the paint problems
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as far as it's hard to spray, i took a 1- 8 hour day classroom class and a 4 hour day in shop class with PPG on painting water base paint and i was good to go. it was pretty much the same as solvent training.
spraying water base requires techniques almost 180* opposite of solvent paint. sometimes it gets difficult because you still use solvent undercoats and top coats with it.