Well, it's the last west bound stop on the main east/west RER line which runs through Paris...and when you ride the escalator up to street level, in front of you is a magnificent chateau in which Louis XIV was born.  Also, Louis XIV was christened in St. Germain-en-Laye...and, oh yes...it's quite near Versailles, where Louis built the most magnificent chateau/castle in all of Europe. 

St. Germain is itself a rather nice suburb with an outdoor market on Sundays, Tuesdays and Fridays...well worth the visit, especially if you're tired of the tourist hordes at nearby Versailles. 

At the east end of the market plaza, take a left on rue Descartes, walk about a block and there is Le Debussy Brasserie on your right.  It's nothing spectacular, just another quintessential French Brasserie.  We had "hot chocolat" , steak and fries and chicken and fries.  All quite good and as St. Germain is a suburb, much less expensive than the same food in Paris...about $20.

On market days, sometimes the market "overflows" to nearby street corners.  The day we ate there, a purveyor of oysters was on the corner selling to a long line of customers.

Food:  A-
Ambiance:  A-
Attitude:  A
Parking:  Good luck...on market days, streetside parking can be found, but it's tough. 
Service:  A
Value:  A+