Duo has some great pastries for special occasions or for a nice catch-up during tea-time. Their pastries are general $6-8 and their croissants hover around $3 each. They are fairly expensive and in my opinion, not worth the price you pay. Yes, their Mont Blanc (chesnut pastry) has a few chesnuts inside and isn't that sweet (which definitely appeals to a lot of folks out there), but after enjoying these sweets once or twice, they start to fall flat and aren't worth the high price point. If anything, the "8" pastry (egg custard) was delicious when warmed up and most worth it for its price point. When I went during the holiday season, there was always a line-up, but also a good number of pastries still out for sale.
If you're keen on getting a certain pastry though, I would call ahead since they seem to be very popular. Also the store itself isn't too large, so you might not always get a chance to sit down and enjoy your tea/coffee/sweets there.