All the subjective parts of the Musou experience aside, I don't think the framework of its combat is particularly good. The hits totally lack impact unless you're comboing 150 guys at once (which you usually are, granted), and the movement's extremely clunky. Most of the time you can avoid feeling that stuff since the enemies are braindead, but bosses make the problems obvious.
DQ Heroes has much, much better enemy variety than any other Musou game I'm aware of, with a few that even fight back sometimes, and there are even things like status ailments you can be hit with. Nice ideas, but ever needing to defend yourself has the knock-on effect of laying bare just how awful it feels to block, dodge or jump.
...I feel like I'm talking more crap than I actually feel. I did enjoy the Heroes games, and they're worth playing just for novelty's sake, though I'd grab 'em on deal if you can, and maybe just skip the first unless you're a real mark for Yangus or the brides. They might have weak combat and lousy stories, but you can tell they tried.
It is fun to hear characters from the text-only games voiced for the first time. I particularly like that Terry sounds like the doubly-edgy offspring of Shadow the Hedgehog and Virgil; as someone who was introduced to the character as a happy kid in Dragon Quest Monsters, his adult self came as kind of a shock.