Windows Vista was a major commercial and technical failure. Commercial, because it is the first operating system in Microsoft history to not be widely adopted and demote previous versions in a matter of months. Technical because a) it was plagued with numerous problems that took too long to be solved, b) it demanded the highest investment in hardware upgrade in Microsoft long history of modest system requirements, c) it failed to deliver a set of key technological improvements that were promised and would have indeed advanced the operating system.
It's quite irrelevant if you like it, and I don't. What speaks for itself was the martket adoption of this operating system from Microsoft that became probably the second biggest flop in their history, only surpassed by Windows ME.