I have had my HD+ for a couple of days now and I am happy with the battery life. Like any battery powered device, it depends on many factors like screen brightness setting, wifi on or off and what you are doing on the device, i.e. watching video uses more power than reading a book. All that being said, I have no complaints. When I saw your question I went outside with my NOOK and found it to be quite readable in bright sun with the brightness setting at maximum. If you stand in full sun, you will get a reflection, but you can still see the screen clearly enough to read what is displayed. An anti-glare screen protector works great to reduce some glare and it also helps reduce fingerprints on the screen.
1) Like Nedrick said, with Brigthness at Maximum Nook HD+ screen is readable outdoors.
2) There's a lot of glare. If you have the sun falling right on it you won't be able to read. You'll have to angle it a bit away.
3) Fingerprints and smudges really create a mess, so you'll need to wipe those off.
The good - with brightness at full and if you angle it so the sun isn't reflecting right off it, it's quite usable.
Keep in mind, this is a LCD screen. It's going to be nothing like an eInk screen. Which means that it's OK but not good for reading in sunlight.
Because I wanted to protect this magnificent screen (the best display I've seen on an e-reader/tablet, bar none) I purchased a non-glare protective screen at B&N. Protects AND removes any glare. Works perfectly!