I
liked Skills and Powers and the other Player Options books.

They were the basis of one of the best D&D campaigns I've ever run.
However, the reason I liked it is why I like 3E
better: it allowed more variation for player characters. 3E gets the rules working better, and allows more development as characters increase in level. (S&P has my favourite version of 2E's non-weapon proficiency system, but 3E does the skill system better as well).
Of course, I was playing with a group of people who weren't min/maxers. So, S&P opened up options to them as to their characters, but wasn't abused by them, either.
I began a S&P campaign about a month before 3E came out, knowing that we'd change over to 3E as I got the books. The cleric of the group was actually a Champion from Spells & Magic, and there were similar little tweaks for the other PCs.
When 3E was released, we discovered that the core of those characters could be modelled using the new multi-classing system, along with the skills and feats system of 3E.
Now, with 3.5e, I'm discovering the joy of entirely new classes, which do things that the traditional 3e system of multi-classing, feats and prestige classes don't handle as well as they might.
Does all of this come at a cost? Absolutely. 3.5e is a very powerful system, but it's also very complex if you want to use everything.
At its heart, 3.5e is a very simple system, but the ability to customise monsters and characters adds a lot of overhead to the game. And then more options are added to that, further complicating it.
For instance, consider the fact that monsters now have ability scores. This adds extra steps onto creating monsters - you need to account for their ability scores. Then, the fact that they have (say) a Wisdom rating means that spells like
touch of idiocy are feasible - and more complexity arises.
That's where I'm conflicted about how good 3e actually is. I love the system for my own purposes, but I worry at how complex it can seem to new players.
The consolidation and simplication of the task resolution rules from 2e seems to have been overtaken by a wealth of options that make the end product... daunting.
Cheers!