Totally worth it. I've got a wild caught male, he's wonderful. More personality than any other fish I've ever had. As interactive as clown loaches are hilarious. I'd almost consider him a companion animal. He's bitten me a few times. He breaks the surface of the water when he sees me coming to the tank with krill. It definitely hurts. I've got a 11ish inch male jag and it hurts less when the jag bites. Jag's name is Adolph Satan. He's earned that name. The umbee is about 5 inches now, still the accidental bite hurts more.
AS far as aggression goes I will say this. First, in my experience, you can't ever predict the behavior of a fish based on species. They are all different. Of course species A might tend to be a little meaner/stronger/more territorial than species B, but in general, you can''t know.
That said, I think the majority of cichlid aggression is highly exaggerated. There are absolutely monsters out there. But In general, if they have space, the right food, and good water, they aren't impossible. I always very strongly believe that fish can be traumatized permanently. YOu ever see those videos of large wild caught dovii ramming the glass when someone bangs the glass? Or taunts the fish/gets the fish riled up by jamming a net into the water? Well. That fish will probably be extremely afraid. People often brag about how smart dovii are, they can even remember people, etc. But usually scoff at this idea. A wild caught dovii, or any large cichlid, is probably fully aware that they are in a glass box. That is to say, they understand that they are restricted in terms of moving to escape from potential harm. A dovii in a 2000 gallon tank will not react to those agitations the same way he would in a 55. So I think that they can be permanently affected by this type of thing. And since there's not much space, they do their best to defend it. Hence *some* mixing problems.
I once had a salvini, beautiful adult male. I traded him in to an LFS at the behest of my spouse, and he was [wrongly] put in a tank with a buttikoferi twice his size. He was attacked. It's been a year. He's still at the store, never has regained his color. He buries himself under gravel when you approach the tank. He's afraid.
Long tangent, but what I mean to say is that they are wonderful, fun, intelligent creatures. The umbee is definitely the most aggressive cichlid for his size/age that I've raised. Normally you see that behavior later on. But I still don't think they are impossible to mix. My umbee is in a growout with a pearl gourami, a moonlight gourami, and a few odessa barbs. Irresponsible? probably, but even though I see aggression, I don't feel like my fish are in any danger. Obviously he will be far too big for fish like that very soon, but even so, i'm not uncomfortable. Now, they do get a lot more aggressive around the 12'' mark. But again, I think it's relative. It's often overstated, and it's easily preventable.
If you like the umbee for his beautiful color and nothing else, don't get one. If you want a pretty blue thing to look at, get a painting. If you are intrigued by their intelligence, curiosity, and bold/active behavior, and you can house him for life given his adult size, then get one. They are mind-blowing creatures in a league all their own.