The first VB I made was really really bad. The oto didn't have anything but the overlap and end of note set. There were english R's and the O's sounded funny. I also pronounced "wo" like you would in Chinese rather than "o".
I wanted the release date to be something cool. It was January 1st. I had been using UTAU for less than 48 hours. (Somewhat related: g-flagged Melt UST)
I also didn't know regenerating frqs was a thing until a couple months in, so when one needed to be regenerated, I rerecorded the sound and stuck it in said first bank as [soundname]2. This made up about a solid third of the voicebank.
About three or four months in, my computer freaked out and someone had to reinstall Windows XP completely. But without service pack 2, so I couldn't change locale and any text in other languages just showed up as squares. I bought a copy of Windows 7 about a month after this incident.
Maybe two years into UTAUing, I had to get a new computer. I made the mistake of not getting one with an audio port thing so I couldn't plug my mic into it. I spent from then until recently using the built in webcam mic.
I also have a terrible tendency to record an entire VCV voicebank and then forget to oto (or only partially oto and never finish) it for two, three, even four years....and by then my voice changed just slightly enough to not be able to rerecord correctly.