Joe Boyd , Oct 14, 1998; 05:14 p.m.
It ain't professional, but here's my opinion.
... the AF-S incorporate the silent wave motor but besides this, are there any other improvements over the AF-I lens? I'm not aware that the AF-S underwent any substantial optical or mechanical re-design (aside from the Silent Wave motor) from the AF-I.
What about the optical and handling qualities of the two types of lenses?
Physical dimensions of the the AF-I and AF-S are about the same and both weigh anywhere from 25-50% more than your current AI-P. So, the tripod and head you're using now should be suitable for either of the AF lenses, unless your current tripod/head only marginally handle the AI-P. The AF-I lens uses the same 39mm filters as the AI-P, while the AF-S uses 52mm filters. The good news is that 52mm filters are easier to obtain than 39mm filters, here in the US.
Is the AF-S faster in focussing?
Yes, although I can't cite any specific numbers.
I guess the bottom line is that unless the AF-S is substantially more expensive than the AF-I, the AF-S is a better deal than the AF-I.
Here in the US, the AI-P goes for anywhere from $3K to $4K, depending on who is selling it. I have no idea what the market is like in East Asia.