I have both 7 speed by 128 mm spacing, and 8 speed by 130 mm spacing. Both versions are very well made and continue to operate smoothly after more than 20,000 km each, with servicing every 5000 km or so.

 Shimano added the word 'Ultegra' to their 600 group set in 1988 with the introduction of the 6400 series groupset.  Also often recognized by the tri-color stripe on many of the parts. 

The Ultegra group was developed to provide a high-performance racing type bicycle for amateur racers and performance oriented sports cyclists. Ultegra features polished bearing races, high strength steels, a striking modern colour treatment and compact high-tech design theme. This approach creates a new upgraded image for a fashionable high quality racing-type bicycle aimed at the performance cycling enthusiast. (1991 Dealer Manual)