Pros:

x You're a badass
x No one expects Shenbae to be able to one shot people. You will consistently have the element of surprise.
x Your taunt is very valuable for an assassin. With some CDR runes you can dash every 6 seconds or so by late game. Very good for catching a fleeing enemy and escaping through walls.

Cons:

x You're squishy early. Very squishy. Nothing more to say other than engage carefully pre-frozen mallet
x Your burst damage is limited to your first 3 autos. If you can get your extra-empowered Q on your enemy they're going to have some serious problems. But after that burst you have to rely on crit to take them out.

Remember: above all else, you're an assassin. So you don't actually need a team. You could 1 v 5. Potentially. If everyone on the team let you 1 v 1 them where you knew where they were but they didn't know where you were, you'd win. Easy mode.
But legit, assassin Shen is an assassin. So when you team engages, dive the back line, slay some ADC's, then GTFO. Because you're a squishy mofo.

Farming is so key in this build. Get 100 farm by 20 minutes at LEAST. The reason assassin Shen jungle isn't better is because he's squishy and has super slow clears at early levels, so his farm is low and it's hard to gank. But hey, you play top lane, just farm your heart out until late game then pick off the unwary ADC or enemy jungler.
Look, if Imma be real with you, you can't do much 1 v 1-ing early. Once you get frozen mallet and become less squishy, then you can start assassinating people. Just for the love of God and all that is holy.... Be careful.

DON'T YOU EVER PLAY THIS IN RANKED YOU BOOSTED BONOBO MONKEY.

But other than that... Thanks for reading this guide! :D
Have fun with the build!