BASH! SciFi Edition is toolkit, first and foremost. If you came looking for a "complete" RPG, you will probably be disappointed, since there is not setting.
That aside, it's a marvellous toolkit. In the span of 138 pages, it covers everything that is needed to run space opera. There's aliens, psionics, cybernetics, a nice helping of guns and sci-fi toys, statblocks for almost every "stock" character type encountered in the SF genre, a collection of beasties and robots, and quite a few starships. You also get genre advice for victorian SF, cyberpunk, pulp-SF, post-apocalypse and sword & planet, along with decent rules for mecha.
Several things deserve special praise:
The scaling rules are top-notch. Characters vs. Vehicles is thoroughly covered by the rules, as is attacking large vehicles with smaller craft. And they don't feel tacked on, they work well.
The equipment section has a nice selection of addons and gimmicks, and deals with combining items as well. Want a grenade laucher on that blaster rifle? No problem. Collapsible quarterstaff? BASH! SF has you covered. An energy sword that doubles as a pistol? Can be done, and we have an arm-mounted energy shield and a jetpack to go along with it. You can build amazing things that way to keep your players entertained.
Finally, the book also has a simple (but working) system for dealing with mass combat, be it in space or on a planetary surface.
There were a few things that irked me, though. One of them was the old cover, which has since been replaced with the one shown here.
Also, the PDF isn't optimized for printing; it lacks the empty page between the cover and the first interior page, and the page numbering starts at "2" instead of "3". Most of you will probably just read it on-screen and not be bothered with the page numbering, but it's a bit iffy to get a hardcopy printed that way.
In conclusion, BASH! SciFi is a great and very compact toolkit. If you need a system for your SF-campaign, look no further.