I am a big fan of the Ultimate Solo Toolkit, so I immediately jumped on the new Sci-Fi Edition. What I found:
Same quality and mindset of the original - it's a one-stop shop for your solo RPG needs. It includes all the oracles you want, character and location creation tables, exploration rules and a basic RPG ruleset if you don't bring one. Add dice, pen & paper and you're good to go pretty much like that. Now personally, I don't use the included rpg ruleset and also tack on another system for expanded NPC interaction, but still find these little pocketmods invaluable since they're so practical (and way more readable than Juiced for example).
The Sci-Fi Edition changes what needed to change and even adds some stuff (also see detailed comparison below) without giving anything up, very nice! Now "Sci-Fi" can be a lot of things, I would say the main use of this Sci-Fi edition is in "into the void" type space exploration gameplay - going somewhere by space ship without knowing where you'll end up. You can do a lot of other stuff, too, but that's where you'll get the most out of it and you'll probably drop half the content if you go another flavour Sci-Fi. And I don't see it especially useful for modern/cyberpunk/near-future urban settings (maybe we'll get even more sets one day? =D).
The differences for those that have the original:
Additional:
Techno-Generator in addition to other word oracles produces word oracle fitting SciFi/Tech (Void, Psi, Quantum, Mech...)
Star system generator
Spaceship combat rules
Changes:
Basic ruleset with psionic powers, ranged weapons and scifi equip.
Encounter Builder heavily adapted for space and un/inhabited planet encounters.
NPC creator table almost double the size (would love this for the basic edition, too!)
Sea travel exchanged for space travel, with separate discovery table
Terrain crawl heavily modified for planet crawl
Dungeon delve tool slightly overhauled for site delve
Unchanged:
Basic oracles pretty much identical
Alien/Monster maker nearly identical
Site exploration flowchart same as dungeon exploration
Hexcrawl nearly identical