Yes, it was worthwhile for Microsoft to release Windows Vista. While there were some bugs initially, and the improvements over the XP operating system are at times hard to see, the changes that have come about as a result make it worthwhile over time. The bugs that plagued Vista have been addressed, and Microsoft knows how to handle its next release more effectively.
No, Mircosoft's release of Windows Vista, which is considered by many to one of the worst versions of Windows that has been released, needed to occur. Through the negative feedback given about Vista, Microsoft has been able to develop software that better meets the needs of their consumers. Subsequent releases of Windows were much better received by Microsoft users.
There were a lot of problems with Windows Vista. Compatibility issues, UI issues, and crashes were all very common. However, there were a lot of under-the-hood upgrades, mostly in memory management, featured in Vista that windows previously didn't have. Without Vista, Windows 7 wouldn't have had the high performance we now expect from a windows machine.
I still have a laptop running Windows Vista. It was not a terrible operating system and it was novel at the time it was released. Vista just had too many permission dialogue box pop-ups. This could have easily been fixed by a patch. I think if Microsoft should regret any of its operating systems, it should be Windows 8.
I had Windows Vista on two computers and I liked it. I never had any problems and thought that it was just as good as the ones before it. I actually prefer it to the new Windows that is out. Vista had everything someone needed and extra items that made it unique to it.