If you demand a transitional to prove one tenet of the ToE then yes.
Logically, to show the existence of something you only have to show one example. Even if Evolution did not occur in any other lineage of organisms, anywhere, only one example of an organism that can be shown to fit a predicted transition is necessary to show that Evolution occurred in at least that particular lineage. This one instance proves that Evolution occurs. If you demand that every extant organism be shown to belong to an evolutionary line then it may be necessary, at least logically, to provide a transitional specimen for each line, but practically we only need enough to show that a pattern develops. At that point, if we want to show that not all organisms are a result of evolution we have to begin looking for evidence that shows a disconnect.
Put it this way, to prove the existence of something, say a leprechaun, all you need to do is find and present one leprechaun. If you want to prove that something does not exist then you have to search every possible potential hiding place, and guarantee that the leprechaun did not move to an already examined place behind your back.
Just as it is not necessary to show every step you take between LA and NY to know that you went from one city to the next and which direction you went, it is not necessary to show every possible transition between two organisms.
If we see you in LA one day, Minneapolis the next day and NY the third day, and we know the possible paths and transportation methods possible for humans to take, then we know you traveled at least one path and used at least one transportation method. If we further know the speed at which each transportation method moves and which paths those methods are limited to we can, based on your departure times from LA and Minneapolis, and your arrival times at Minneapolis and NY we can calculate the most likely method and path you have taken. The more points we know in the path and the arrival and departure times the more accurate our estimation of the types or transportation and paths taken.
The way we can identify that you are you at each point is by identifying a number of 'diagnostic' features which make up your physiology, morphological traits. This is the same with fossils. We identify features that are exclusive to a particular clade and follow the changes, or retention, of those features as we travel though time to the terminal organism of the lineage.
Although there are many more than just Archaeopteryx fossils available to show the sequence between dinosaurs (which is a rather large group) and birds (another large group), there are a number of traits which do not belong to modern birds, but do belong to dinosaurs, and a number of traits which do not belong to dinosaurs that do belong to modern birds that Archaeopteryx has that we can be highly confident that Archy is a valid transitional between dinos and birds.
If we track the trait changes in the dinosaur clade through time, and even if you doubt the absolute dates given by radiometrics, the relative dates are pretty easy to verify, we see that early dinosaurs had no bird-like features but later dinos, especially theropods, had a few bird like features and other features were becoming more bird-like as time went on. There was a pattern emerging.
We also see in birds, traits which were changing from Achy-type (sorry) to more modern bird-like in bird fossils following Archy. Even though we class Theropods as dinosaurs, and Archaic Aves as Birds, the changes within those clades indicate a specific path taken. Archy is midway between those two clades along the same pathway (although Archy was likely a cousin to the organism on the direct path).
This pattern was observed, not just in the Theropod/Aves line but many others.
Good post. :-)