I was added as an AU on a few CCs with high CLs ($10k+, high compared to what I had at the time). Since then, I've been approved for two $10k CCs, one $5k CC, and all of my existing CCs have raised my limits a bit. I went from $8k in total CLs to almost $40k (not including the AU lines) since being added in June 2008. As with all things, YMMV.
5/11/08 FICOs: EQ - 551
8/6/08 FICOs: EQ - 659, EX - 663, TU - 683