When it comes to components...

Anyone?

Shimano does trickle down its stuff to a point... For instance, the latest Ultegra looks a lot like Dura-Ace from a couple years back, but as you move down the product line you'll still be getting cheaper/heavier materials than if you were using the actual Dura-Ace stuff of the same design.

So as looks go, yes. As far as materials, etc. probably not.

Ultegra, Dura Ace are almost the same other than some of the materials used making DA lighter.  I would consider 105 the minimum entry group set if you are going to race and/or train hard.

Sora and Tiagra use a different system altogether and are best suited for recreational riders though lot's of people use them if that is what they have and are just starting out.  Sora and Tiagra will probable never "trickle" to 105 or above.

Gregkl, thanks for thr response to this and my other post.

My guess is the trickle goes from DA to 105 but the Sora and Tiagra don't have the same quality no matter what year you're going to compare them to. Stamped Vs machined, high nickel content Vs pot metal, that sort of thing.

That's all just from what I've looked at and found but it seems to hold true with the major brands that have both a high(er) end set as well as a department store set.