I would say that their model seems to be working for them so far, and I'm not sure if the loads are indicative of what they have been experiencing lately. That being said, I know their european flights are regularly pretty close to full loads (I use them quite a lot GLA-ALC when visiting my folks) so maybe they are subsidising this route at the moment to get a market share (I think they have only been doing Glasgow to Stansted for the last few months).
I hope they make a go of this route - they seem to be expanding into new routes (Stansted being the most recent "departure" from their europe model), including the launch in 2006 of a GLA-Orlando Sanford route offering three classes - a no-frils economy with 30" seat, a premium economy with 34" seat pitch, and a business class with 50" seat pitch. Having had a look at their one-way "business" class, its pricing around £380 each way, which for a 50" seat cant be too bad. Obviously its a very niche market - dont see them taking any business from BA or the other big carriers on these routes, but for holiday traffic it offers a nice alternative from the crappy charters out there.
All my praise of them aside, I'd still fly BA everywhere if I had the choice (instead of my work dictating we fly cheapest carrierd) and if they flew where we have offices. Oh for the long lost days of my Silver card