I'm surprised at how few threats some of these lists are running, particularly covertgo's. I'm not arguing with the decklists -- you guys are far more experienced and have had way more MD success than I have.
However, how do you usually end games? I can't imagine either planewalker's ultimate is too reliable. Woodland Bellower is a pretty big body, but it's the only one in the deck so any hard removal shuts that down. I really like Winnower but it doesn't strike me as a "I win now" sort of card in the same way as say, Gaea's Revenge. Do you just incrementally build up card advantage then chip them down over a long period? How often does shadows of the past do enough damage to seal the deal?
As I was typing, I realized I didn't see Erebos's titan in the list. With so much removal plus the land-grabbers to make BBB feasible I'm sure it's a great card vs most decks.
Still though, I'm curious how you finish your typical game.
Liliana's Ultimate is actually really easy to get because of her +2 only needing 3 activations, but I rarely use it because her - ability is so good in this deck. Nissa's ultimate has won me a lot of games but her +1 provides so much advantage that you're usually winning regardless. Her - minus ability is nothing to sniff at either: while I'd rather reach for her ult a timely 4/4 can turn the tide, especially against aggro. The singleton Gaea's Revenge does so much work it isn't even funny and my addition of Graveblade Marauder adds another win con as well as shutting out the more aggressive decks that may outpace us.
This deck isn't about a single definitive win con though - it's about complete control of the board state and building advantage through the mid to late game so your Nissa/Lily/Graveblade, hell even the incremental damage build up from your Fleshbags etc can seal the deal.
The walker control deck is deceptively simple to pilot, but knowing when to use which card and why will be the deciding factor in a lot of games. I truly believe this is quite possibly the strongest all-round deck in the game ATM, but knowing your match-ups and your primary targets for removal is going to be massive in most games. Hell, if you could sideboard and games were a best of three I'd say this deck was practically unbeatable given the current pool.