I've heard it's "decent" but nowhere near as good as the other Sony systems in Ford's lineup. It's too bassy, the highs are bright to an almost painful level and it has poor imaging and detail.
That's why I've already put together a list of components I'd like to eventually get for the Focus (Note: Emphasis on SQL. I am not a "boom boom" person) This would be a two year project simply because, well, it's incredibly expensive... but I've been spoiled by good sound (I have a cambridge audio/paradigm system at home) so it'll be hard to deal with the Sony stereo.
So, this is what I've decided on. (Keep in mind that I mostly listen to progressive rock/metal and I cherish a perfectly neutral sound, so the sub I went for is more for accuracy than power...)
Signal Processor (pretty important because I'd imagine the EQ curve of the Focus is like a roller coaster):
JBL MS-8
Front Speakers:
Focal K2 Power 130KR
Rear Speakers:
Focal Performance PS 130
Center Speaker: (to be powered by the processor)
Focal Performance PC 100
Amp:
Focal FPP 5300
Sub:
Focal Utopia Be® 21 WX
I'm planning a sub box to be integrated where the stock sub box would be. If all goes according to plan, it should look a lot better than the cheapo plastic box they use with the sony system. I'm going to map it out in pro/e this weekend.
The price I'm aiming for, installation and everything, is around $4250