Oh, those fruit salad trees that are like, cherries, peaches, nectarines and plums (or some combination of stonefruit) all on the same rootstock?
Meh...Well, I am a fussy home orchardist, but if I had seriously limited space I suppose I'd get a couple. Here is what I would be concerned about:
-The grafted scions (i.e., the fruit-bearing branches) may not be well-matched with respect to vigor. In theory, they should all be equally-matched and produce about the same amount of fruit. In practice, you might get one branch that grows really really fast and takes the majority of energy from the rootstock, giving you tons of, for example, cherries, but only a couple of nectarines. You can control the vigor by pruning...sort of. How much you have to prune will depend on the vigor of the scions, which you will have to find out the hard way.
-Most likely they will all be disease-resistant modern commercial varieties. This will affect the fruit quality, in that the very sweetest, most aromatic and juiciest peaches/nectarines/plums/cherries are not often the disease-resistant commercial kind that were originally developed for production, packing and shipping cross-country. Now, a tree-ripened peach, even of a commercial variety, is invariably better-tasting than a peach picked half-green and sprayed with ethylene to ripen in a grocery store warehouse, but still. If you were looking for, you know, the Ultimate Nectarine Experience, you're not gonna get it from a nameless commercial variety, as a general rule.
-You will indeed have to spray it. Probably a couple times per year. And now that I think about it, you will have to hope very much that the grafts have been thoughtfully placed. Fruit trees are usually pruned in the following shapes: goblet, Christmas tree, or flat against a wall. The positioning of the grafts is going to dictate how you wish to prune this thing, because obviously in this case, if you need to lop off a badly-placed branch that is, say, hindering air flow through the branches and inclining the tree to fungus, you will lose a whole type of fruit rather than merely a branch. Your other option, in that case, would be to spray the heck out of it and hope. I would imagine that they place the grafts in such a way that you would get a goblet tree, so if you wanted some other shape you'd be outta luck.
Me personally, if limited space is an issue, I would look into espaliering or cordoning several trees flat against a southern wall/fence. But that may be more pruning than you want to do.