Summary: Potentially, a great game, but not worth buying as of now, before the cheat issue is fixed.
After spending some time reading the reviews left by others, it occurred to me that I have very little to add to the said in the negative reviews below.
Basically, I prefer multiplayer games, since NPCs (no matter in what game), overpowered as they may be, are hardly a match for a human player. Thus, this game never interested me as a single-player one.
To really start enjoying it, an online 7DTD game requires quite a lot of time. When playing online, expect spending several evenings (up to a couple of weeks) in order to stop starving and set up a more or less protected base, which will finally allow you to start having normal game fun. However, at this very moment, one should expect cheaters to come and ruin the whole thing. They will shoot you through stone and walls, change ownership of your clam blocks, loot your locked crates, and eventually blow up your base. Some of them will be as nice as to offer some kind of explanation of their actions, as these two gentlemen (or ladies?): http://cloud-4.steamusercontent.com/ugc/29604125252900333/DB5B0FE4B0B0ECBDBF7A46663B5C8F2476260C63/
, but most will not. So, after having spent long hours on scouting/hunting/gathering/planting/crafting/reading/building etc., etc., in some ten minutes you end up losing your base, stuff, food, health (since they keep killing you on respawn), and further motivation to continue playing this game. It happened to me thrice at three different servers, and I think this is it for now.
So, YES, 7DTD has the potential for becoming a great game. And NO, there is no reason spending your money on it now, when it is so easily hackable. What I suggest for those who think about purchasing 7DTD is waiting until final release, and buying it only if there are no reports of hacking of such scale.