yes i had similar thought when i first tried oopsies Ange, but the first recipe i did had a little mustard in, i got used to them by second batch and decided to try them just plain without any mustard or flavouring, after bread isn't flavoured, and i preferred them. I must admit too that they don't taste great with every filling, my friend puts anything in hers but i have only really tried burger, cheese, ham and ham n cheese, i used to put a bit of butter on but now i just use a spread of mayo on each one, tastes better in the sandwich, at first i put butter on them and put mayo in them.
i just store them in an air tight container, they don't last long enough to go off, but my friend said she puts baking sheets between them and freezes them, i have not tried that.
The trick with them is to whisk the egg whites stiff, i use a hand mixer for it and then fold that into the cream cheese, egg yolky mixture they lose a little of the stiffness then but not too much. i then spread it onto my whole baking sheet to make a big rectangle, once baked peel that off then cut them into 6 slices.
I think they do take a little getting used to, and my friend said so do mims but try and try as i might i can't get used to them, i get about half way through one and the texture just gets to me. when oopsies cook they do smell like cake but quickly lose the cakeyness. once you master the oopsie the possibilities with it are limitless, my friend does all kinds of sweet creations with hers, might be worth mentioning that her diet is suffering and she is now going to cut out so many sweet treats.. but once in a while they can be a godsend. she puts splenda, cocoa and coffee in them and makes a scrummy looking tiramisu, i haven't tried it or swiss roll yet.
Its also like anything you make the first time seems daunting and it appears to be hard but the more you do it the easier it is, at first i thought the process of making them seemed odd, i don't think my first lot of whites were stiff enough either, but they have always come out ok. my friend even missed out the cream cheese once and they still turned out okish.. lol