"But there's no demo!" is no excuse. Go read a review, or simply don't buy it.
You know what? When I hear about a game that I might like, I'll get my hand on it and play it. I'm not gonna wait months for a demo (
which might not be free anymore soon), not gonna read any review by corrupt reviewers, fanboys or some guy who has his own personal opinion, not gonna wade through overpriced Ebay auctions hoping to spot a reasonably-priced copy, and especially not gonna listen to some do-gooder on a random forum who thinks he has the right to judge or tell people what to do.
And don't get me started on DRM, disc-checks, copy-protection, online activation and constant connections, missing LAN-multiplayer, the quality of games nowadays, repetition, forced hardware manufacturer/publisher intros, terrible translations, censorship in certain countries, bad support (patches, bugfixes), the criminalization of customers or the fact that nowadays, you don't own games, merely a license to play them that can be revoked at any time.
No, I'll simply play it. And if you got a problem with that? Sucks to be you.
If they couldn't test it? Hm... they would test it in the other way? i.e. Demos or look for forum opinions?
Are you serious? I don't know many people who would rely on a demo to judge whether to buy a game. Especially since demos are released too late (if at all), offer too little, don't tell you whether the story is crap or what you can expect regarding support for the game. And most importantly, it does not tell you how multiplayer will be like.
And forum opinions? They're far too personal. Besides, fanbois everywhere.