Yeah, I don't see how any modern sign shop can roll with just using an app like Flexi. I'm more accustomed to using CorelDRAW, but I increasingly have to get a lot of work done using Illustrator. It's all due to certain features and effects that get baked into corporate branding and other kinds of customer provided artwork. Gradient fills that use transparency and blending modes related to transparency are especially prone to failure. The stuff can fall apart in unpredictable ways when opened directly in CorelDRAW. Some effects aren't supported at all (free-form gradients, gradients on line strokes, etc). That kind of stuff really falls apart when an attempt is made to port it over to Flexi.
