More important to me, though, is the increased resolution. D5000 has 10.2 megapixels, while the new D3100 has 14.2 MP. That's a huge increase in photo clarity and this is crucial if you plan to use Photoshop to crop images at all.
That's not true- the D5000 is 12.3 megapixels.
IMO, the increase in resolution is not that great from 12 to 14 for the average shooter. If you're trying to be a pro, maybe. But then you should be looking at the pro bodies that are doing 18+ MP.
It comes down to what you need your camera for... the OP suggested video is important, so that may be his deciding factor. But then again- what kind of video?
I just got my D5000 and the video is great for me? Why? My other hobby is golf- camera is great at taking swing videos, from a tripod with a fixed manual focus for a video that lasts 3 seconds- perfect! The average video shooter will want more than the D5000's video features offer, though.
As far as a still camera, let's not forget that this is not the D5100 it is the D3100- there is a reason they decided to put the new camera into that line of models- because it is more like the D3000 than the D5000.
You still have to look at the cameras other features, menus, and capabilities. I get the impression (obviously without actually having seen or used a D3100) that it is more entry level than the D5000 is (which is also entry level)- if that makes any sense.
As these cameras cross more into the realm of "imaging computer" than camera, photographers have to deal with what us computer guys have dealt with for 20+ years now... do I buy/keep/use what I have or upgrade to the next version? If you do, you will constantly be chasing "the next version."
I've discovered it is better to be on the leading edge than on the bleeding edge.
Look, the D5000 is a great camera. So is the D3000, D3100 (hopefully), the D90, etc. There will always be another camera model coming out.
But I guarantee I can take a great picture with my old Minolta Maxxum 7000 and a roll of Kodachrome 25! How do you take a great picture? F8 and be there.
And what you'll find is that F8 at 1/125 is F8 at 1/125 no matter what camera you're using.
Who knows, after you trade in the D5000 for a D3100, what happens in 3 months if they come out with the D5100?
Then you'll be kicking yourself!