Flying KABQ to KDEN, descent to 240-170-150, then warned not to exceed 250 kts, complied with the 250 kts max. After landing critique exceeding 250 kts on several occasions- I thought that this applied to 100 only not 150, or am I mistaken.

In high altitude areas such as Denver you are not to exceed 250 kts. once you reach 150.

I'll guess your xing restriction said "...at and maintain 150, 250kts...". In any event, unless you've called minimum fuel or have declared an emergency, approach controllers will want you at or slower than 250kts while in their airspace.

Doug,I often don't get a CR, only a "I need you down in..". No one says anything about 250 below 15000, so one just has to know before they reach approach space they have to be at 250. So I make sure I stick DEN into the plan now.