I'm a recently designated MAI. I work in a large U.S. market and I've been here since graduating college in 2004. My first job was w/ an MAI w/ a small shop (just him and his wife). He did primarily litigation work, though occasionally he'll do some other things. I worked for him for about two years before moving on to a small national firm (if that exists). The workload there was almost solely production bank work. I now work for one of the large national firms.
Was it worth it for me to get the MAI? I'm not really sure. The way I look at it, no bank is going to hire a non-MAI firm for any kind of large project. But as long as the boss has an MAI, he can bring the work in and other appraisers can complete the work. This is typical of national production shops, as I'm sure everyone is aware. It doesn't matter to my boss if I have an MAI or not. I'm not really going to bring in much additional work that he couldn't already bring in. So as long as I want to work for an MAI firm for the rest of my life, I don't need to be designated.
I have frequently made the argument that my bosses haven't really wanted me to be designated. Sure, it adds some stature to their staff and they can say they have a few different MAI's working for them, etc. But it also empowers me. It probably makes me more difficult to deal with. I'm going to want more money, I'm going to have stronger opinions, I'm going to have something to say about how the younger appraisers are being trained, etc. So my bosses always encouraged me to take classes, take the comp, complete the demo and become designated. But I also thought they realized it wasn't in their best interest for me to actually get the designation. If I were running my own shop and had a few junior appraisers working for me, that's certainly how I would feel.
So was it worth it for me to get it? I don't know. If I wanted to go open my own shop, I would absolutely need it. No one is going to hire me without it. If I did get any jobs w/o the designation, they would kill me in review and find a reason not to hire me again. If you don't want to run your own shop, I would say you don't need it. But I'm sure most people on this site are running their own shops.
So what do you want to do w/ your career? If you're running your own shop, or you're planning to in the future, I would think you'd have to have it. You certainly would in a large market like mine.