I'm very happy with it, but I have one question. In the past, I have always removed the battery if I am going to be working using AC power for a couple of days, because I've heard that it is bad to continuously charge a battery.
However, this time I am using Windows 7, and notice that the AC icon says 99% available (plugged in, not charging).
Does this mean that leaving the battery in on this model won't hurt my battery?
Well, I believe that it was the heat that was actually "shortening" your battery life when you are leaving your battery in the laptop while charging.
I would recommend you to remove the battery from your laptop if you are going to use your laptop on AC adapter for prolong usage. However if you are going to stop using the battery for a long time maybe like a few months or even a year, you should keep it charged at around 40% before you keep it aside and I wouldn't recommend you fully charging it when you are going to store it for some time.
You are well advised not to fully charge or discharge modern batteries. So running the machine on power with the battery in may shorten its life.
Best to treat it like a cell phone battery -- you don't let it run down and if you lead a busy life you probably just charge it long enough to top it up for the next day's use.
There are various strategies for running the battery in when you first buy it, like charging it fully twice (as I recall) but as you have been using this computer I wouldn't concern yourself with that now.
It sounds as though your HP's design has anticipated the previous problem of overcharging/overheating batteries by continuous charging. But as per my original reply, 99% is probably too high a charge, so perhaps better to leave it out when using the laptop on power for extended periods.
I suggest to try to never let it get above approximately 75% charged.
I've owned two laptops. The first was always fully charged, and the battery needed replacing within a year. The second laptop is going on 4 years on the original battery, and has very rarely been charged above 75%, and has no significant loss of battery life. Limiting the charge was probably easier for me than it would be for you, though, as my laptop had a feature that would allow you to force it to stop charging at a 75% charge (or 40%, if you were so inclined to limit it that low). Apparently it worked.
It's just the way Lithium-Ion batteries work. Ideal charge to store them at is 40%, although this severely limits the amount of charge you will have when you actually need to use the laptop on battery alone. The higher a charge they are kept at, the sooner they will need replacing. Same with temperature. Prolonged exposure to higher temperatures (such as those that result from gaming on a laptop) will result in a need to replace the battery sooner.
Modern laptops are designed not too overcharge Li Ion batteries. Older laptops would continue to trickle charge the battery once it was fully charged.
The main enemy of Li Ion technology is heat. Even at room temperature the chemical structure of the battery is continuously breaking down/ aging. At higher temperatures (e.g. in a hot notebook) the effect is exacerbated. Some extremists would suggesting storing Li Ion batteries your freezer! Obviously condensation forming when "thawing" out the battery is a bit of an issue there... :-)