VideoReDo Plus is an MPEG-2 cutter. It will allow you to cut MPEG-2 while only rendering a few frames at the cut points. It can be handy at times, but isn't a replacement for Vegas Pro. It's just another tool in the box.
The upgrade adds h.264 and other functionality that I've managed to get along without for many years. Since I spent more than $26 at Chevy's last week for margaritas when I got bored, I bought the upgrade.
VideoRedo doesn't rerender frames except a couple at your cut points.
That is the same as smart-rendering AVC/TS/MP4, something Vegas doesn't do.
More importantly, all transport stream errors (from broadcast or camera source) are fixed and resynced, along with reindexing and properly closing long-GOPs as necessary.
There is also a commercial cutter and timeline cut-and-join editing, and a handy queue for batch processing.
VideoRedo is not something you could compare to Vegas, since it is a muxer that lacks second-tier editing functions. It is a preprocessing tool that is normally used before Vegas or an encoder such as Handbrake.
Absolutely indispensable if I am recording broadcast programs from satellite, cable, or OTA.
I mainly use it to trim and remove commercials from recorded TV broadcasts, just what it was primarily intended for. It is also useful to tidy up videos, as MV10 mentioned, and to re-wrap your video into another container, e.g. .ts (transport stream) to .mpg (program stream) without re-encoding.