I had high hopes for PD, but so far I'm less than half-way through PD on Special Agent and I'm not enjoying the experience much at all.
For what it's worth, the game really comes alive in Perfect Agent mode. So many of the subtleties of the experience are lost in Special Agent mode to make it easier. Fighting the Skedar is a great example of that. In one level, you start with just a knife on a Skedar ship with enemies everywhere. You'll quickly learn that your knife can be thrown into the back of a Skedar's head for a one shot kill. In Perfect Agent, those guys are bullet sponges, so it's a revelation when you learn it. As you work your way through the level, you'll come to realize there is a "right" path through the place and it requires perfect timing and precision to make it through.
The rest of the game is very much the same way in Perfect Agent, though the first few levels aren't the best showcase of it. The game takes a lot more thought and planning than GoldenEye did and that makes it a very different experience. Perfect Dark is more of a stealth game where you should be working your way through levels out of enemy sight, whereas GoldenEye is closer to a run 'n' gun, though some of the stealth stuff is still there (Bunker comes to mind).
I can see why Perfect Dark wouldn't be as appealing to most as GoldenEye in the single player campaign, especially in the lower difficulty segments, but that's largely because they are fairly different experiences that, in my opinion, won't necessarily appeal to the same people.
The only other game that reminds me of Perfect Dark is, surprisingly enough, Hitman 2. While not a first person shooter, the stealth elements, objective-based mission structure, and versatility of the experience make for something extremely memorable. Of course, we needn't forget Perfect Dark's challenge mode and multiplayer modes, which put it in a different league. Spec Ops mode in Modern Warfare 2 did a great job of updating the Challenge Mode concept introduced by Perfect Dark and improving it considerably. And of course, the multiplayer mode of Perfect Dark improves what was introduced in GoldenEye making it a much better choice for bouts with friends.
I can see where people would draw parallels to other first person shooters of the time. Surely Rare was influenced by some of these other experiences, but clearly they are all different and unique games, not the disjointed hodgepodge of concepts I believe you are describing, adadad. I concede to the point that the mission objectives are completely unclear and that provides for some definite frustration. For me, at the time I played through Perfect Dark, I had a whole high school summer of doing nothing to complete the game and part of the experience was discovering what each objective was while playing through the missions. For something like the retrospective, that part of the game is unwelcome because it hinders getting through it for discussion purposes.
If Perfect Dark didn't have its multiplayer component, I think it would be a love it or hate it kind of experience.