All of the above are actually normal things for a battery to do.
The best way I can think of this is to have you think of your battery like a balloon. If you fill a balloon up to 100% (as in, one more puff of air and it pops) then it's going to be a very... fragile balloon. Not a very safe place to be. It's much better for the balloon to be at about 90% capacity, cause that gives it some wiggle room.
Batteries are in fact designed to work the same way. The charger will get them up to 100%, but it's not healthy for the battery to stay at a full 100% all the time. So the charger lets it drop to somewhere between 90-95% (depending on the manufacturer) and keeps it steady there.
Now, most people would see that, and think that their charger is broken. They'd go nuts, yell at sales clerks, etc. So.. the manufacturers have programmed the phones to report 100% at first and then steadily drop down until they've caught up with reality. It's.. a bit of a lie, but it keeps a vast majority of inattentive customers from complaining about something that is actually designed to prolong the life of your battery. This is why the first 10% always seems to go much faster than the rest.
So. Everyone in this thread, and all the varied reports, have nothing to worry about. That's all well within normal operating parameters for a battery. The variances are due to different manufacturers and their various beliefs in what's a comfortable level to stabilize a battery at.
To the OP: Charge your device every night, if that's what pleases you. It's designed to last longest that way (i.e. will last you years instead of months) and will ensure that when you start your day, your device is topped off and ready to keep up with you. Studies I've read claim that a battery that is never allowed to drop below 50% will last 3 times longer over the years than a battery that is regularly drained to 0. Obviously it's not -bad- to let it drop to 0. It's just better to keep it from doing so. (Note, this is only true of the newer Li-Ion batterys found in cell phones. Older Ni-Cad batterys had that memory problem that is so infamous. Cell phone batteries do not)