I remember the original TV series mainly as being completely, utterly, awesome.
The effects weren't particularly sophisticated, but they fit well enough, and never detracted. You didn't really notice them.
This is more than just a good story distracting one from the visuals, I think; the effects guys did a pretty good job with their limited means, and often those primitive effects really managed to communicate the atmosphere and feeling intended. They did this much better than Dr Who's effects ever did, in my experience: With Dr Who, one almost always had the feeling "ok, this is some guys on a soundstage", but with HHGttG, often it somehow really did seem like they were stowed away on a Vogon spaceship. I'm not really sure how they managed to pull it off as well as they did, though I suppose even in the category of "low budget BBC SF efx" there's a range of budgets...
.. and the hand-drawn "computer" animations were great. Together with the incredible music, they were a real highlight.
There were some lowlights, of course; I remember the scenes on the Heart of Gold as being pretty bad.
[Watching your clip really brings back the memories of the complete bliss of watching that on TV way back when... just hearing the music sends chills down my spine... :]