The Death Collectors failed totally to engage my interest, yet more monsters with silly voices and Sylvester McCoy shouting a lot.
By contrast the one-ep story Spider's Shadow, on the same BF release, seemed to me a really neat time/space paradox with Seven trying desperately to avoid being caught by the bubble as it collapses.
Peter Davison is cruel in the extra tracks of The Boy That Time Forgot: "So imagine my surprise when I saw that they had brought Adric back, only this time he is being played by ... an actor!!!" Indeed, Adric survived the crash of Earthshock, and is now in charge of a prehistoric kingdom of intelligent scorpions. But don't worry, Nyssa, he has decided that you shall be his queen. The Doctor, however, is to be eaten. The story treads on uncertain ground but does it pretty confidently, helped immensely by Andrew "Manuel/prank phone calls" Sachs as the aged and crazed Adric. Unfortunately John Pickard returns as Brewster at the end, but you can't have everything.
The Doomwood Curse was my favourite of this run. Charley and Six, having visited a far-future library, find themselves caught in the fictional world of Dick Turpin. This is territory Who has occasionally dipped into, most memorably in The Mind Robber, but done with great conviction here, especially by India Fisher who plays Charley Pollard as a gangster's moll. Excellent fun.
Both Kingdom of Silver and Keepsake seemed to me unusually dull even for Seven/Cyberman stories. Apparently they fit into the continuity of BF's sequence of Cyberman plays; I might give them another try in that context.
In summary: The Doomwood Curse and The Boy That Time Forgot are good, the others not so much.