In the paragraph before the puzzle you say Nc7+ cannot be stopped, whereas d5 would stop it quite easily. It's not a mistake in the puzzle, I just thought I'd say that...
Now the puzzle itself. It unfortunately requires white to play a blunder, and so it can't REALLY be considered a puzzle... at least not in my eyes. I'd be interested to hear some other opinions.
Good puzzle, as you said.
(6. ...e5 fails to 7. Nd6#.)
d5 does not stop it... d6 allows the knight to simply take it. e5 allows Nd6#.
Perhaps I should post the variations.
Edit: OK, after d6, we have Nxd6+ Kd7 Nxf7 forking the queen and rook.
Ok, sorry about that.
The second bit of my post still stands.
White did not play a blunder. After the puzzle ends, they are still equal in material (because of Qxe5 Nxe5 gaining the bishop back).
The whole point of the puzzle is that black doesn't lose material and/or get checkmated.
Fair points, but next time rephrase your first sentance to make things 100% clear.
What are you, the grammer police??
Just enjoy the puzzle and ask questions, get clarification as you see fit.
No need to be snotty.
Nice Tactic to save material.
Also interesting is that white has his choice of either bishop or the knight in the forced trade scenario.
I would not take light squared bishop as it is hemmed in and you would just allow him to develop rook. The knight does not seem attractive as it will just be replaced with other knight.
I would probably take dark bishop and then drive off knight with f4.
What was result of game and how did it continue?
Fair points, but next time rephrase your first sentance to make things 100% clear.
What are you, the grammer police??
Grammar police. (I'm in the spell-squadron of the literacy brigade.)
I apologise, Icy. It seems everything I said in my original post was incorrect. That'll teach me to try to analyse something at 10pm! 
No problem Nytik ^^
I ended up winning. It was a tight game though.
Fair points, but next time rephrase your first sentance to make things 100% clear.
What are you, the grammer police??
Grammar police. (I'm in the spell-squadron of the literacy brigade.)
I apologise, Icy. It seems everything I said in my original post was incorrect. That'll teach me to try to analyse something at 10pm!
For someone in the spell-squadron, it's odd that you missed the original misspelling of sentence.
Incidentally, I'm in the logical-pedantry department.
Next time it will presumably be a different puzzle, so he shouldn't rephrase his first sentence to make things 100% clear, he should just phrase his sentence to make things 100% clear.
I suspect rephrasing this puzzle's sentence and using it on a different puzzle will actually serve to make things even less clear.
Here's a good puzzle from a game I played recently. Black cannot stop white from playing Nc7+, forking the king and the rook, but he has something up his sleeve...