I was using Adobe Premiere, and to preview a transition, effect or superimposed title, you had to "make movie", and wait watching a red bar move across a window while it rendered an avi. file just so you could preview it.
The only editing systems that did real-time previewing were hugely expensive hardware boxes, or later computer cards.
Suddenly Vegas 3 arrived - it did real-time preview from its software. Years before any other system, including Final Cut on the Mac. You could also throw video of any format or resolution to the timeline, and it played the lot seamlessly.
Vegas was still relatively unknown for years, then thankfully Sony, who bought it and many other gems (such as Sound Forge and Acid Music) from Sonic Foundry and now Magix, have recognized the quality of this software and it survives in Version 16.
I have automatically bought every version since 3.0, not so much because I needed the new features, but more to support it's future, which continues .