I think the kit overall is an excellent, fitting design. As with any rework, some numbers or timing tuning will probably be required, but the kit has a good basis. They kept the most iconic things about her (ult, resets) and added even more resets (Shunpo resets without kills now). They also managed to do that in a way that lets her get in and out of the same fight without having to get a kill but without being an automatic out, like LeBlanc W is.
Katarina's W is actually a highly flexible skill that rounds out her kit. It lets her guarantee a return Shunpo target. It gives a small move speed boost for positioning (or a bit of general map movement). If you are feeling aggressive or have a reliable jump out target, it can be cast after going in for more damage potential and further mid-fight Shunpo reset. If nothing else is going on, it helps with waveclear.
I think the main reason W can feel unfulfilling is that you know it can do all these things, but can only really do one or two at a time. I think people will grow to appreciate it as they play more and realize what it actually can do and learn to optimize its use.
Overall, the daggers serve as the "windows of power", where she can be powerful if she can set up and use them well, but weaker if the enemy can play around them. The delay is there to make it more fair to the opponent but is a bit jarring if you are used to playing her old instant version. Time will tell if this ends up too much in the favor of one party or the other or if it ends up in the middle. They also fit thematically, since she's always been throwing daggers, unlike Shen, where the giant spirit sword came more or less out of nowhere (he used swords, but not that kind).
I think the feeling of reward will come as players learn when/how/where to use the skills effectively, but W will remain the glue skill that rounds out the the kit more than the obvious power skill.
