Which means that the 787 is still basically still only an artists impression...

Dreamliner indeed.
How much can an artist's rendering actually weigh?

Depends on the paper...

I havent heard of any weight problems in the 787. Its a small aircraft, supposed to replace the 757 and the 767...
...If it works out I think its a better design than the A380 simply because it has great range and doesnt need a lot of runway, much unlike the A380.
Well your first statement says its replacing the 757 and 767, yet in the second statement you compare it directly with the A380, which is replacing nothing, and is competing in the 747 market, of which Boeing have had a monopoly for 37 years.
I have heard that airports like Heathrow are putting in extra work in expanding their taxiways just for the A380. That seems a little over the top to me.
When you're one of the biggest airports in the world you make your airport fit for any potential airliner, particularly if its an Airbus or Boeing.