Is this camera worth the money?

Is the Nikon D3100 worth approximately the £400 that it sells for?

I have had a few people tell me that it is fantastic, and others try and put me off. But i'm not sure whether they are trying to put me off because i know that they used to want this one until they went for a cheaper make and maybe now regret it (just by the way they said it made me wonder whether it was them or the camera that is the problem!) But i'm unsure. Apparently if i wanted to take a quick photo without a lot of arranging the subject then the photos blur a lot? But surely changing the shutter speed would help reduce this if i were to change it?
I also do a lot of videoing and was told that it goes out of focus extremely easily, is this true?

More to the point, is there a huge noticeable difference between the Nikon D3100 (£400 ish) and my current Fujifilm Finepix S1800 (was £150 at the time)?

I'm just a bit confused with people telling me different things for different reasons!
Huge thanks!

Added (1). Thank you Ian -

If i were to buy a lens more specific to videoing would that make quite a big diference to the focusing? X

DSLR cameras often go out of focus when using it as video because the lens isn't always auto-focusing. You focus once, and then if the subject or your camera moves, you have to refocus.

On the Fujifilm, you are stuck with the one lens, but not with the Nikon, which makes it superior. You can put on much better lenses.

And yes, the D3100 is worth the 400 that it sells for. If you want a camera better than the D3100, those are more expensive.

If you change the shutter speed to something less than 1/120, then the subjects won't blur as much. But for that, you will have to read up and do research on how DSLR's work.

Any DSLR is a better camera than your superzoom Fuji. Image quality, speed of use, and options all go to the DSLR.

The focus issue has nothing to do with the lens, it is the camera. Not all cameras support continuous AF in video mode. A new lens will not change that. You can check the reviews of the camera and see if this one does or does not support continuous AF in video mode. If it does not, then you need to plan your shots around that fact.

The D3100 is worth it if you know exactly what you are doing. That means you should know photography. If not there will be no difference with the pictures you take using the D3100 and the S1800.

With respect to videos, it would be best to get a digital camcorder to do the job. DSLR's were never meant to do video hence you will find the lack of controls annoying in most instances.

Yes.

In my opinion, no. For £400 I could buy a Canon 1D mkII or a tatty 5D, now once you're experienced enough you start to really feel the difference between a top of the range camera and an entry level camera.

Both the 1D and 5D put almost all controls at my fingertips, and the massive viewfinder is always a bonus. The 1D has 45 autofocus points, and it's just so unbelievaly crisp, and it's built to be bulletproof. The 5D is a little delicate, but still a lot stronger than a D3100, plus the 5D's full frame sensor is nearly double the area.

That's just me, cameras and cars are quite alike. Why get a brand new city car when you can get a top of the range Merc (with a 6-litre V12) for the same money.