Well, considering that this game is being offered for free, the only real question to ask yourself is whether it is worth the short download time and small amount of space it will take up on your hard disc. If you don't want to read my review, here's the short answer; yes, it is. What are you waiting for? Download it!
I'll keep this review to the point; BASS is a game with a wonderful story, although in my opinion the story could have been fleshed out a bit more. It's set in a city which is hundreds of stories tall, and feels to me sort of like a composite of the Los Angeles in Blade Runner and the city from Brazil. If a cool sci-fi story set in a place like that sounds like your cup of tea, than this game is for you.
The graphics hold up fairly well, and if you run it through the included emulator you can tweak the graphics to be a little smoother. The voice acting is all very good, although I have to wonder how a bunch of British people (and one American guy) ended up populating a city in Australia.
Of course the most important part of any adventure is the puzzles, and BASS has some really good ones. Most of them are very well thought out, but there are a couple that are nonsensical (and nonsensical puzzles are the bane of many adventure games, imo). One in particular involves launching a small animal into a pool of water with a catapult to destract a guard. What? Still, over all they are very interesting and make sense.
Anyway, why are you still reading this? You should be downloaded Beneath a Steel Sky.