So, my team of Truant Durant/Skill Link Cloyster/Rough Skin Garchomp finally lost, with a final streak of 546
The team and its strategy are detailed at length here: http://www.smogon.com/forums/showpos...postcount=1903
I lost to Black Belt Harimao.
He led with Forretress. I used Entrainment on the first turn, he used the remarkably irksome Toxic Spikes. Since being poisoned would significantly impair Cloyster's set up, I decided to switch to Garchomp, whose Lum Berry would keep it unpoisoned while setting up. Garchomp set up nicely and kileld Forretress, but it laid a whole ton of hazards, including a second layer of Toxic Spikes.
Next out was Infernape. I was too clever for my own good and used Protect to block the lead Fake Out, which left me completely cold to the next turn's Encore. I should have just Earthquaked the first turn and been interrupted by Fake Out, knowing that after Fake Out, the AI would have Infernape try (and fail) Encore the next turn, letting me kill thanks to Rough Skin breaking the sash on the Fake Out turn. I didn't, and so ended up losing Garchomp.
Durant came back in and Entrainmented before dying to Flare Blitz, leaving me with Cloyster as my last pokemon. Cloyster came in, ate Spikes and Steath Rock damage and was poisoned by Toxic Spikes. It set up one shell smash on the Infernape's loafing turn, and then KOed with Icicle Spear, taking more Toxic damage in the process.
At this point, I needed something I could KO at +2 or I would lose to Toxic. Unfortunately, the third poke was Probopass, and it was game over for me.
Frustrating to misplay so deep into a streak, but I had some good luck earlier, including getting a desperately needed crit after a bad misplay on a Speed Boost Yanmega (a huge threat to my team in the lead), so I was due.
A few notes on my overall impressions. First, in terms of speed-power balance, this team is wonderful. Battles go pretty quickly, one rarely needs to check the trainer-pokemon chart, and the team is remarkably consistent. It's obviously not as consistent as Yadazhai's team (gotta love that 892 streak!), but battles certainly go a lot faster.
Second, as you go you start to get a much better feel for which enemy pokes are actually threats. A lot of things look like they could cause trouble with a lead Protect or Fake out but either never use it, or can't do much after using it. I felt better and better at predicting the AI's approach as I went on, and feel that were I inspired, it might be fun to write up a guide to each possible lead a la Peterko's Cloyster/Garchomp/Suicune Guide.
Third, though I lost to hazard setting Forretress (a poke that I accurately noted as a threat in my earlier detailed write up), as I got further in the streak, I expected to lose to some sort of Brightpowder lead. Missing with first turn Entrainment is remarkably frustrating, and even worse was the one battle where I missed AND the opponent used Substitute to really rub salt in the wound. (I think it was Dugtrio 4, but I've played this streak over many days and it was a long time back so not positive now). Somehow I won the battle (mainly thanks to good matchups with the opponent's other pokemon) but it was clear that at some point this sort of thing was going to catch up with me. There's fewer accuracy lowering items in the Subway than the Frontier, but still enough to cause issues on long streaks.
Fourth is that Rough Skin Garchomp is the real deal. Rough Skin made several battles noticeably easier, and even gave me a double KO win in a 3rd pokemon matchup of my Garchomp against an opposing Focus Sash Garchomp (my getting stuck in this close of a situation caused by, what else, multiple misses on a Brightbowder pokemon earlier in the match). For Subway purposes, Rough Skin is a gigantic upgrade over Sand Veil for pretty much any sort of strategy, and if you haven't gotten one yet, I highly recommend going to the dream world and catching a Gible. You won't be disappointed.
I may try to play around with Entrainment some more (perhaps with my silly "two extra life" Substitute/Giga Drain/Focus Sash Lilligant), but honestly, much of the design space for Entrainment teams is already played out. It's going to be very difficult to build something more consistent than Yadazhai's Whimsicott/Durant/Dragonite (particularly given how, as shown by Jumpman, Whimsicott is probably the best crippler in the Subway and mono-attack Dragonite the best post-cripple sweeper). As far as a trading power for speed, I find it hard to imagine a Durant cripple team that's much faster than this team, given the inherent speed limitations of alternating Protects and the fact that Cloyster already incorporates the fastest set up move in the game. Perhaps the right Garchomp replacement could improve consistency slightly without reducing battle speed (allowing a new team to be superior in at least one dimension to teams already posted) but I've already done a fair bit of Garchomp theorymoning and its specific advantages are hard to replicate. Accordingly, it may be time for me to take a break from Durant for a bit.
Given how much I'm enamored of Rough Skin Garchomp, perhaps revisiting Garchomp/Suicune/Ferrothorn is in order...