My Outback uses press studs, surely that is the worst idea ever? It is only a question of time until they give way really, and without having a good closure all the way around dust gets into the tent, much like Symon's. Mine have two string ties per side to tension, and these are necessary to get the studs done up, especially at the back.
I have used the zippered kind, and whilst I can understand your frustration, still think it is the best setup. I will definitely be replacing mine with a zip around apron when the time comes.
In saying that, I would like some wide webbing straps with quick clips fitted across the cover, maybe two each way, sideways and lengthways. I would use these to strap down the load (as I would get a generous cover to allow for more stuff to be carried on the bed when moving day by day) and also allow you to get the zips done up by removing some tension from the cover.
You could easily retro fit straps like these I reckon, and even one each way might suffice?