7 Days is definitely lowbrow sci-fi; I don't contest that. It IS, however, a very interesting show. It is a rare series that is able to set up its mythology and continually twist it every episode. They were always changing what the future is. What could be done about the time line. How to change the time line. What the device could do. What other devices could do.
It is also interesting to note that this series is rare in that it dealt with the notion that navigating time was a difficult task. Every other incarnation of a time machine in sci-fi stated that it was difficult to make, but here it is - let's go!
I wish I could have seen more of it to give a better evaluation, but my local station dropped it very early.