USU5 like the 2005 original uses -p-123 (retained for compatibility), there has to be some method of passing the products_id/cPath through to the osCommerce script .. there are other seo url contributions that use pure text .. BUT .. pure text is an intangible/unreliable whereas e.g. products_id/cPath are unique as dictated by MySQL autoincrement.
So the answer to the first question is that they are essential.
Regarding path based uris ... www.mysite.com/my/great/product/p/123 I have purposely NOT included this feature for two reasons ..
Firstly it is effectively a lie .. that directory structure does not exist and the best of the bots are not stupid (well they are they are bots but you get the idea).
Secondly it is now suggested that Google bot is stepping back through directory paths and as these paths are not real is likely to create problems.
I thought about it and I know that software such as Drupal use such paths but decided against it.
Thank you for your response! That was very insightful and informative. For the path based uris, would the second example I gave be feasible? Having it come out like /catalog/category-subcategory-product.html?
The reason I ask - say my site sells candles, and they are displayed/named by scent. So when you click on, say, the 'apple' scented candle, the URL is just /catalog/apple-p-123.html, which doesn't help with the SEO too much. But say that 'apple' product is in a 'candle' category, having it come out /catalog/candle-apple-p-123.html would help more.
Let me know what you think when you get a moment.
Thanks again! =)