I like the Knight of Swords. I think it depends on your own make-up how you see him, as well as the context of the reading. Some people thrive on those kinds of realisations; some don't.
Is he like the Tower? Not to me. But he may seem so to some folks, though they'd have to be pretty concretely entrenched in their ways, I believe, to get that kind of reaction. It can depend on the state of mind you're in at the time, too, but Tower-like is not what I get from him. Remember that some people do get hysterical at the thought of change at all. I think where the Tower-feeling may come in is seeing any change of plans or change of perception (cos that'll happen with this character) as a disaster.
Both cards have a lot to do with light, but the changes that come of the Knight of Swords are not the same as those wrought by the Tower. But if you're not fond of change at all...
I've had the meeting of the minds experience indicated by him before--it does take things to a whole new level, and quickly, but doesn't have that shattering things you value to ruins quality to it.
It's going to depend on the situation, and just as importantly, on the person. When I'm reading for myself, I've fallen into calling him the Knight of Light, because that's who he is to me--and the KoS people I tend to meet--they often embody that Knight of Light quality. So for some folks, certainly, it's great.
I don't want to veer off onto an esoteric track here, and I could, easily, because for me that's where this character lives, but no, he's not always a negative card, not by any means.