Take the tall fly tower - raw concrete at the moment, but soon to be given a sub-Barry treatment at the insistence of the heritage lobby. Previously, there was a stumpy apology for a fly tower, so low that it severely restricted the shows that could be put on. The backstage areas, formerly cramped, are now gargantuan and can swallow entire fully assembled sets with ease. There's a whole new private fiefdom of ballet rehearsal pavilions up on the roof, one of which will double as a public performance space. Getting round all this takes a while. It is a complete arts township.

How many of the gawping tourists realise that this large and confident building complex is happening almost in spite of the managerial chaos that has engulfed the Royal Opera? Here's the rub: the new House will be able to do far more than its resident companies can now afford to attempt. It is designed to allow up to 15% more opera and ballet performances than previously in the main auditorium, plus 100 extra performances each year in the Studio Theatre. But as the world now knows, this will not happen. The ROH chairman, Sir Colin Southgate, has announced that, among much else, he must open the luxurious new House in 1999 with one-third fewer performances than were previously put on under extremely difficult circumstances in the old place. The Studio Theatre may be mothballed. For this, they have paid £214m? This paradox will no doubt exercise the mind of the executive director appointed last week, Michael Kaiser of the American Ballet Theatre.

But, chin up. London is not alone in having problems with the opera. Amsterdam had full-scale street riots over the building of its new house, which is still popularly known as the "Stopera", after the name of the campaign that tried, and failed, to halt it. Paris has had trouble learning to love the new, weakly postmodern Opéra Bastille - not least because most Parisians understandably prefer the old and glorious belle époque Opéra Garnier. But in London, in a typical and probably correct case of nostalgic British compromise, we are not abandoning the old place to build the new one - though this did not prevent a succession of planning rows and redesigns. It all culminated in a successful lottery bid for £78.5m - a third of the total - in 1995, and final planning permission in 1996.

And lo! Once money and permission were granted, the new House sprang from the ground as fast as rhubarb in Wakefield. It is on time and on budget. It is supremely ironic that this magically efficient process has taken place at the very same time that the management of the House and the organisation of its operating finances have been in a state of near-total meltdown.

Touring the House today, you realise the magnitude of the task. This is design on an industrial scale. The opera house, when finished, will be effectively a factory. It will employ up to a thousand people, manufacturing exquisite forms of performance art. The opera and ballet companies and orchestra will rehearse in new rooms on site - one of them capable of taking a full-sized set that can then glide onto the main stage. And the Royal Ballet will for the first time live there. Down below, many complete, fully assembled sets will be stored and shuffled to and fro invisibly on mechanised trolleys, like an aircraft production line. The equipment accounts for one-fifth of the entire budget.

To build the new ROH is a logistical exercise requiring military standards of forward planning and execution - which, against the odds, it has received. Dixon and Jones, as they scramble round the site, now seem almost incidental to the process they have instigated.

What gets them most excited after all these years is their modern contribution on the far side of the restored Floral Hall foyer, where the aesthetic shifts into cool 1990s modernism. "Hey, look," says Dixon with glee. "They're putting the glass in!" And they go and coo over the glass like boys with a new toy. Back in the 1980s, the pair had at least one toe in the postmodern camp, and the drawings from that period show it: but the toe has been withdrawn. Their designs have been stripped down, almost to the point of austerity, and they are the better for it. This is no simplistic modern design, however: there seem to be endless little short cuts and back doubles through the building that retain plenty of the eccentricity of the original.

The new Royal Opera House is better than all right. It shows all the signs of being very good indeed. This may be no comfort to those who want to find even more ammunition to fire at the hapless ROH board, but for the rest of us it is good news. They may be having problems with the software, but the hardware is spot-on.