It is the lowest of the high runes. High runes have roughly the same values of other high runes, but some are more valuable than others. Um is cradled in between the middle runes and the high runes, which makes it worth just about any valuable Unique (such as Jalal's or Shako), but also worth high runes, such as Mal (best trade value), Ist or Jah (best usage value), and Ber (which is arguably the best of the high runes before Zod).
60 for Ancients. 75+ is recommended to get the best of the possible experience, based on monster levels, and ease of difficulty in killing monsters (as in, not using 16 Potions to kill one champion).