Venser, the Sojourner is my favorite card, because it speaks to me from multiple angles.
First and foremost, I love blink effects. Something as small as a blink can change the way a lot of things operate, by repeating enter-the-battlefield triggers, rescuing your mind-controlled or perpetually-tapped creature or other permanent, or even just giving something pseudo-vigilance. Or, perhaps in a cube, you can do something nasty like blink a wincon and proceed with a wrath - or even nastier, an Upheaval - and continue onward uncontested. It's a lot of versatility, making Venser's first ability elegant, even though it's incredibly simple.
Venser's second ability is perhaps a bit confusing to a control deck trying to abuse his +2 with the likes of Wall of Omens or Mulldrifter; why would you ever use this ability? I always believed this is because Venser was designed for the BantPod deck when it was standard legal, a midrange monstrosity that abused etb triggers and eventually amassing a huge board. With Venser, you can build up advantages until you can simply overwhelm your opponent; a -1 with "Creatures are unblockable this turn" could just as well read "win the game" in the right deck. I enjoy cube, and find Venser doesn't need to use this ability to be good, but having the option allows him to fit in more decks than many other planeswalkers who don't have as straightforward abilities as "Draw a bunch of Cards". For this reason I think he trumps most other guys outside the Lorwyn 5. Both the +2 and -1 can work together, but they don't need to.
Venser's ultimate is incredibly powerful - a little wonky, to be sure, but powerful. Spells giving you free, colorless exiles is exceptionally good, and cantrips like Preordain suddenly become incredibly valuable. If you have a Batterskull on the table, you're in amazing shape. And this isn't an ultimate that takes forever to get to, either.
Venser is far from the best card, or even best planeswalker in MTG. But, all three of his abilities are potentially powerful, which lead to enjoyable experiences every time I play it. Because Venser's abilities require a little bit of planning, I find that deck construction with him becomes quite interesting; some already good cards gain additional value, some strategies suddenly have an entirely new angle when he hits the field. Being able to think ahead and see real benefits of that planning make playing the card a very rewarding experience.
I think not necessarily every game, but I predict some opponents will really punish me if I throw this at them. Like "yeah man I got you now, oh word you got archon of cruelty out off your treasures ok I concede". I think just from a cube design perspective it's good for the deck(s) that want to use the card sometimes use the treasures meaningfully, so I'm just mindful of whether there's sufficient 'or something' in 'equipments or something' in the draft pool.
thought of an alternative: I've seen some people who include aristocrats and persist packages add cards like Mayhem Devil. There might be some overlap here.
I think what's interesting to me is just reading what other people anticipate using this card for - I think it speaks to its versatility. Because, my initial instinct was W/x control casting this on X=3 to blunt an attack and have tokens left over, but we can also discuss this as a protection spell first value second. And beyond that, I see any X spell that generates tokens a useful top-end for any ramp deck.
I think it's not particularly strong in any one department, but this is three different decks it can fit into. This is why I like it.
I probably speak for most people when I say it's just not really what I'm looking for at the moment, but I can absolutely conceive of cube lists where it it's a fun card.
Something I like about this set is that there seems to be a high density of cards that interact with multiple archetypes. I find myself more drawn to cards like Sniper from a cube design standpoint because it makes me feel like I'm tinkering with lots of tiny parts that can fit into a deck identity I wish to play. I feel this would contrast with a card like Bosejiu, which feels more like just a strong card that doesn't care too much about what you're building. But ideally my list will find room for both.
Do you feel any pull towards either style of card? Would you prefer to see more of one than the other in future sets? I ask because I feel now more than ever, lists can afford to become more divergent due to there being a wider variety of powerful and interesting cards - some of which may be entirely dependent on the synergies found within a particular cube. If this phenomenon is real, I wonder how it could impact future card discussion. There will always be home runs in the New Card Discussion but I feel like a lot of the time I can't give a simple thumbs-up or -down ... it's like, "Well this card is good if you also have x, y, z ...". I dunno, just curious if that's something you ever think about.
W
Farewell
Lion Sash
March of Otherworldly Light
The Wandering Emperor
U
Mirrorshell Crab
Mnemonic Sphere
B
Blade of the Oni
Dokuchi Silencer
Junji, the Midnight Sky
R
Fable of the Mirror-Breaker
Ironhoof Boar
Kumano Faces Kakkazan
March of Reckless Joy
Ogre Helm
Rabbit Battery
Reinforced Ronin
Twinshot Sniper
G
Careful Cultivation
Roaring Earth
Teachings of the Kirin
plus
All of the Channel lands
Colossal Skyturtle
Kaito Shizuki
Eater of Virtue