I did own VIVVO at one point then later sold my license on. I liked it and still do to be honest, it looks like a very good CMS and has a very nice default layout and style. But what I found what the software is "dog slow" to run. I would'nt like to say how it fairs if you use one the more advanced cache systems it offers, but using the default was terrible for me. Very slow at doing anything with it, painfully so. Real pity, it's very much a true CMS and has some great SEO features and more besides, a very good article system. I would have stuck with it myself but the running speed just lets it down too much. It's also too expensive.
I've also owned and used SubDreamer, the old version that was purple styled. The new version now looks interesting, I was looking at it a bit ago. But you have to weight them both up against WordPress that's not only free to use with great backing behind it, but a brilliant CMS/Article system.