on 1.4 it takes forever to load my library. Its about 150gigs, and i use itunes. it eventually loads, but it take 3 or 4 minutes... sometimes more... sometimes less. when I use 1.5 or 1.6 it loads quickly... but for gigs, i stick to 1.4, cause its more reliable, in case i happen to have a bad mp3. any suggestions or ideas as to why it takes so long to load? i'm on a powerbook.

The time taken to load is simply a reflection of the size of your library. 150gigs is a lot of music.
As you have noticed, 1.5 gives a massive improvement in reading times.

My suggestions

1. Learn to trust 1.6.1, rebuilding overviews will help you weed out the troublesome mp3s

2. Cut down the size of the library you use for gigs.

I agree with nobspangle.