It's pretty good, but you should first do a fair bit of research first.
This is because if the enemy has musketeers, you are pretty much as good as dead.
The firearms are a new weapon type, previously not seen before on the other games of the series (excluding the use of mods), They are extremely strong, but are more inaccurate than a bow & arrow and they take a while to reload.
Introductions of firearms are not a total letdown, as you and your little army can also have them too, but it is always annoying when its near the end of a tough battle and you lose rather abruptly.
Even so, it would not be realistic if firearms did insignificant damage.
After looking through this rather annoying 'flaw', the game itself is rather good, bringing a whole new world for you to conquer.
Many new features have been added, most for the better, but you will have to get used to some additions.
In conclusion, the game is good, but you will have to decide if it worth getting something that you can get with modifications of Warband.