Yep, Flexi is my "main" program.
I started in this business 3 years ago, and at that point had never (seriously) used Corel / Illustrator / Flexi.
I started out with demo's of all of them.
Flexi was WAAAAY easier to get up and running and producing useful material.
The topic has been discussed here many, many times.
Many folks find it buggy / crash a lot. I've not found this to be true.
Flexi charges for every little update - I HAVE found this to be true..
I think a lot of folks find Corel and Illy "better" for a large part because they know the program inside and out, and have been using it for years. I really think most of those "other" programs are design for many applications and uses, whereas Flexi is specifically for the sign industry.
My experience is that for more complex designs, I often have to use several programs (not the least reason because with digital printing, rasterized elements come into play so much...) but for my fast, day to day, bread and butter work, there is just no comparison whatsoever to Flexi.
Another program that I "discovered" here actually, is Xara.
Its vector based, but has some very, very cool features - things that I used to struggle with photoshop with, I can do in seconds in Xara. My biggest problem with it, is the import/export features give me a lot of grief. It's really inexpensive too!