Neckties stay cinched, cashmere sweater sets remain in pairs, and no one appears to have punched out for the day at PS 450, a spot tailor-made for an after-work rendezvous. Don't be fooled by the namewhich refers to the Park Avenue South address and not anything juvenilethis lounge is all grown up. Aiming to soothe weary workers, the multiple rooms are lit with an orangey sunset glow that counteracts the effects of florescent office lights and broadcasts music as unchallenging as any Starbucks compilation. The main bar provides plenty of tall tables, where you can order a couple of the not-so-tiny "small plates" from the menu. The braised short-rib nachos ($12) and the mini tilapia fish tacos ($11) are exceptional and easy to share with colleagues. Forget about preparing for tomorrow's meeting and unwind on the low upholstered seating in the middle alcove; just don't get too relaxed and forget to order your liquor. The "perfect" margarita ($12) is strong, though not exactly perfect, while the Park South lemonade ($12) with real fresh lemonade and Belvedere Citrus is tart and tasty. Last stop is the back room, with a second bar and standing room only to facilitate late-night mingling. Any cocktail that your heart desires can be ordered by the bottle ($48) and serves 4 to 6 people, which makes you wonder how many PS 450 receipts end up on expense reports.