On the notion that upB OoS is no longer as safe as it once was with the 3.5 update:
It's still a useful tool but cannot form the basis of countering high-pressure characters such as fox and falco, but is rather overshadowed by the power of b-reverse grenade, which tends to put it right in the hitbox of either spacie's dair/shine hitboxes, which then leads into a techchase (most often off of a missed tech since it's an irregular activation that they have trouble preparing for). That said, it's an easy punish for sloppy and/or mindless play. On the subject of the matchups themselves, I recently played the strongest Fox of our region with Snake and gave a commanding control of the situation, 2 or 3 stocking him in most games and dropping very few. This is due primarily to the power of the DACUS as an approach option, Snake's fantastic grab game (aided by the appreciable boost grab), and the power of the C4 stick mixup. Many of my kills basically went as such: DACUS into techchase, where I dair into a JC grab, which leads into another techchase where DACUS covers techs away, dair covers tech in place and jab resets any missed techs, and a C4 stick soft-punishes any platform escapes (because they tended to shield and wait to punish a hit on shield). This is further aided with the lower endlag on C4 sticks as well, which allows an easier interpose of it instead of a regrab. From there, camping the Fox out with grenades and mines is entirely viable, seeking a single stray hit to convert either into a techchase or into a C4 KO outright. Additionally, discoveries I've made in the MASSIVE hitlag of up throw leads me to the knowledge that Fox will be KO'd easily at 80% by the simple combo of up throw, up air, C4—absolutely huge given Snake's massive vitality against Fox's KO options, ranging from high weight and semi-fast fall speed to grenade's capability of overwriting knockback values such as Up Smash or back air. I qualify all of this by saying I've played this Fox since I first started playing PM Snake, and I actually do better after 3.5 than I did before. He has knowledge of Snake's tools and weaknesses and attempted to abuse them, but I simply played to the matchup and took advantage of his playstyle. This is likely due to my shift in mindset regarding Snake's options, given Fair, F-Smash, and Up B all received nerfs, whereas C4 gained something of a utility buff (but a KO nerf) and DACUS became far more natural with the Z input gaining a frame of lenience. The Fox matchup is extremely even—perhaps even in Snake's favor.
That said, Falco is still difficult due to his ability to gimp Snake and pressure him from afar with lasers. cautious recoveries (including mixing up recovery as well as you can) combat the former whereas the crawl (and its tilt, which still leads into a grab consistently) combats the latter. Most of the same strategies of the Fox matchup still apply, with the addition of beanwolf's suggestion that Falco is garbage while recovering, with Snake having all the tools to abuse the fact. Falco is in much the same boat as Fox in this regard, being an equal to slightly advantageous matchup for Snake.
