A lot of reviews bring in outside reasons for giving this game a low score, which I find a little odd. I have to say, I think THIS GAME, RIGHT NOW, is wonderful and just as fun and interesting as the original Planescape: Torment and is absolutely worth your money.
I expect most people are going to be familiar with the style of gameplay, so specific to Tides of Numenera, the systems that allow for spending pool points to accomplish things you're interested in really work well - you can pick and choose what goals you have in mind, rather than finding out mid-conversation or mid-combat that you can't follow that choice. Combat, I could take or leave, just as I could in the original. It does some interesting things and honestly my takeaway is that it's best to spread out your points; concentrate on one area if you like but don't short-change your other aspects.
I found the characters fascinating as well; one thing the original Planescape: Torment and Torment: Tides of Numenera do well is to have regular people struggling to survive in this bizarre landscape, where something you find while scavenging might kill you or make you a god. Your relationships are all about dealing with this aspect of the world, and you have choices about how you deal with it and how you help your companions deal with it.
I think anyone who's enjoyed Planescape: Torment will enjoy this game - it is rich with imagery and depth, and demanding in all the right ways. Personally, I think it surpasses the original in a lot of respects, but even if you don't think so, it's a damn good game.