Isn't such a thing not bothering you setting he bar pretty low? I mean, at lest in live presentations they should have Explorer load a page that would not crash it.
I hear that windows 8 beta has the nasty habit of freezeing often. Makes those who devleop apps for these things refere to MS products like in the "good ol days".
If the tablet would have burst into flames, sure let it bother you. Its the same with other gaffs, like 360 Conference last year, or the (rather funny) Wonderbook not working at Sony's E3 this year, or how about Zelda from the Nintendo conference not working basically at all? These things are minor and should not bother people, nor keep them from buying into these products.
Now, if the MS tablet/PC/Surface/Thinggie was in production right now and did this? Sure, but my Smartphone locks up from time to time and I do not see any reason to get another one.