It is pretty nice, and the models get better every day. As a caveat, I must say that there are LOTS of things to consider when doing research with iPSCs, mainly related to how accurately your cells represent actual human cells. For example, I work with iPSC-derived neurons and any change in the process of maturation of iPSCs into neurons vastly changes the properties of the final cells. Also, neurons and other cell types take long to mature from iPSCs. In the case of my cells, it takes around two months until they are at a stage I can use for my experiments, and they have to be maintained for that long and lots of things can go wrong.

All of this is, of course, also a problem with ESCs, but not with animal models. If human genetics are important for your experiments, iPSC models are almost the only choice you have. If there is a good animal model for the disease you're studying and organism physiology is more important, then animal models are better.