I just bought 3 of those, i love them! Those are the W model which means they are more of a flood light, They're also available in the S model (the spotlight version). They are definitely worth it, in my opinion. Plus they are extremely small and you dont have to plug them in, which makes shooting in small spaces and shooting outdoors extremely easy.
It will work, but it's not going to provide the best looking light source. I have a few of the and I always try to use it as a secondary light source-something that can match the color temperature and provide extra lighting to an already lit environment. Even with a lower color temp, the light with a diffuser comes off looking a bit harsh if you try to light directly.
Surly they will be better then the £100 soft boxes I had?
btw these lights dont sit on top of my camera. They will stand up on tripods.
LED lights tend to look very different from tungsten lighting, which tends to be a lot more forgiving. Will it be better than what you had before? Depends on how big your softboxes are. If you're using the LED light with no diffusion and your softboxes are larger, then you'll have a smaller light source and it may look more harsh.