This is most probably the lightest bag I have ever had the pleasure of purchasing. Sometimes I fear I forgot to pack my bag, because when I pick it up it feels light as air, like there is nothing in it....and then when I check, there are my books and laptop! I am a graduate student who's been searching for a good bag for...3 years now and have had no luck until now. For some reason, women's bags always have those tiny little shoulder straps that really dig in to the shoulders. I needed a bag that had wide straps, back support with ventilation, and didn't make me feel like I was carrying the world over my back. Within days my constant bachache from my horrible previous back receded. The side pouch for water bottles actually holds on to it, and the bottle doesn't slip. There is nothing to keep it standing though (its only flaw)...Also, not to mention, the color and design is very attractive..it's even better in person! I highly recommend this bag!!
-Osprey quality (and warranty)
-Very sturdy top handle (might not fit on bathroom stall hooks easily)
-Zippers seem to be quality and loops on pulls are nice
-Padded laptop and tablet compartments (even on bottom)
-LOTS of room (but can be compressed with straps)
-GREAT organization with many compartments (see photos)
-Front grab handle, if you find that useful (This is what seems to separate this pack from other women's specific 27/7 packs. The Nova is almost identical to the Celeste, but with a front stretch pocket instead of grab handle. All else being equal, I'd prefer the Nova with an easily-accessible pocket.)
-Whistle on sternum strap (though it would be hard to use if you were using the strap as intended, since it's built into the clip)
-Two water bottle holders (rather standard now, but I like that they are large enough for the wider bottles, but also could be compressed to secure smaller bottles)
-Great color options
-Straps. I hated them. They are thick and stiff (perhaps they would "break in", but I'm not willing to chance it) and dig into my (not very large) neck (and yes, I know how to properly adjust and wear a pack). They also scrape my arms if I'm not wearing long enough sleeves. Since I walk ~10 minutes from car to office, often in sleeveless shirts without a high collar, this will not work for me. They seem to be exactly like the straps on my friend's unisex Nebula in both size and shape, (see photo) so I'm not sure why Osprey put them on a women's fit pack. (This doesn't match what Osprey says on their website for their women's specific fit (pasted below). This is the biggest strike against this pack. I realize packs fit different people differently, so maybe they will work for you. I just can't wear a backpack that has straps digging into my neck and scraping my arms.