It's odd how different my experience seems to be than everybody elses'. Everybody seems to be clamoring for S-Burn nerfs, and I think nerfing it as-is could very likely make for a more boring game.
Note: This post got a bit more rambly than expected, and I'm not overly experienced at the game. Plus I alt-tabbed out of a fight and want to get back to that. Forgive me if my thoughts jump all over, or I state something wrong.
I like S-Burn right now. I don't feel like the sector is "small" or any such thing - there are dozens upon dozens of systems in default-options sector (each one that you can explore - you don't *have* to fly in a single direction for 90 days for a thing to have "more space") and I still sometimes sit and stare at my screen on S-Burn while holding shift to get around. If something feels small it's because there are only 2 dozen or so inhabited systems by a few factions that don't try to expand. I most definitely don't want to have to alt-tab because of huge travel times or sit and stare at my screen as I hold shift for long periods of time. That isn't content I find fun, or immersion-improving, or whatever else. S-Burn majorly helps avoid such situations.
I also use E-burn sometimes. A lot? No, but I don't feel like I'm supposed to constantly use it. S-Burn destroys my maneuverability while in, stops my fleet to activate, and slows my acceleration - sometimes I need to e-burn away or in a different direction really fast to escape somebody. I sure am not instantly turning around and S-burning in the opposite direction without huge risk of them e-burning into me before I can actually build up the speed to escape.
Honestly, I shift it on/off a fair amount because of how much it decreases my turning ability. And when I do that when enemies are near, I'm also thinking if I'll be able to build speed back up before they e-burn into me.
Embolism suggested making shift speed up time more - this is a possibility I can support, if S-Burn is "nerfed." I'm still hesitant to say so though - warnings can make it safer, but they also make traveling more irritating (suddenly stopping time) or if you disable them, much more dangerous as it reduces your time to react. Then you're choosing between "irritating unexpected tops" or "extremely dangerous to reduce the time you spend waiting as a player." I don't think either of those are very great.
On "Burn" as a stat - I think it still has a purpose. It's primarily made "meh" (if it indeed is) because of how speed bands interact, and how the AI is limited.
1) The "Speed bands" of ships are about about 8-10 (Normal), 13-15 (E-Burn), and 18-20 (S-Burn).
2) The AI doesn't have access to the third band, as it cannot S-Burn.
3) The Third band is the fastest band, and even the slowest speed of it is decently faster than the highest of the 2nd band.
4) Burn speeds are capped at 20.
This means that if your entire fleet is 8-burn you can still escape a "fast" AI fleet, so it doesn't even matter that your ships are innately slower. Then with the 20-burn cap, the 11-Burn of Falcons and whatnot ends up being *mostly* useless - either you hit the 20-cap, or the extra benefit it provides is already unnecessary. It does help when you're in an E-Burn "chase" since it puts you above the AI, but those are not overly common.