It depends on how you target the ledge. It just takes practice, more than any other teleport.
Always come in from below the ledge and you'll have the same vulnerability as anyone else.
I swear every time I see people having issues with mewtwo not grabbing the ledge out of teleport its because they are doing it from very close and almost horizontally where it can bounce for other characters that teleport too.
Tuesday's Smash direct has me really excited and I decided to visit these threads again. Although I might main Cloud for a bit and just secondary Mewtwo (unless he gets some huge buff).
Just wanted to point out that you're both either wrong or don't understand what the original poster was talking about. It's been proven that every character has a few vulnerable frames before he grabs the edge out of Up-B, every character. But depending on what character you are your Up-B might be safer or weaker, plus the overall length of these frames seems to vary for different chars (although I don't know if this has been proven).
Chars like Sheik, have a hitbox, a windbox and her frame becomes smaller when teleporting, which means her hurtbox is smaller which means she is harder to hit. Couple that with the fact that it's just a very few amount of frames and it makes it really hard to hit a Sheik when she's ledge grabbing out of Up-B. Although it's pretty easy for chars like Doc, Fox, etc which can "float" with a multi-hit move right at the edge (Watch Larry vs any Sheik when customs were allowed or Nairo's Dr vs a Sheik).
Mewtwo has NOTHING to defend his Up-B, he seems to be the char with the most vulnerable frames AND he has a huge ****ing hurtbox allowing chars like Mario to be able to hit him with an D-Tilt from on top of the stage even if the Mewtwo perfectly spaces his Teleport. The Mario just has to be very accurate about his timing.
It's a huge glaring weakness of the character that is almost never exploited by the opponents because no one has deep Mewtwo matchup knowledge (plus it's still a very time intensive punish, specially since Mewtwo should try to be as random as possible about when he is going to Teleport and he has things like Side-B plus a huge floaty Double Jump to help him force the opponent into mistiming the punish). But trust me, I've fought against Mario's who have punished my recovery 3-4 times in a row with D-Tilt from the stage even though I would drop down and Double-Jump into random Teleports to try to throw away his timing. And it's not Mario only, Mewtwo's hurtbox is so big that I wouldn't be surprised if almost every char had some move that could hit Mewtwo from safely on top of the stage.
The only upside is that you when you get hit in this way you get your double jump back instantly (even though you didn't finish the ledge grab, you still get it) which most likely means you'll be able to try some OTHER kind of recovery that doesn't involve Teleporting to the ledge. But the opponent will still be able to intercept that recovery and **** you up.
Anyways if Mewtwo gets buffed expect me to hang around for a while, but otherwise I might just go into the Cloud forums, depends on how fun he is to play. I haven't really played Smash in the last 3-4 months, been too busy with work and **** but I am kind of excited one of my fav chars from my childhood is being added (and the possibility at one of my other fav chars getting buffed). Now if for sme weird magic trick (some might say cruel joke) Goku gets added then I am never touching Mewtwo agaoin xD. Goku is my #1 man. Not that I expect him to be added but Cloud just ****ing threw all my logical thinking out the window.