About a year ago, I got a new LDE203X battery and AC19V90K1 AC adapter for my Inspiron 6400. I ordered from LaptopCharge.com, and I'm satisfied with that choice, the site and the items.
Basically, there were three choices for getting a battery and AC adapter: Dell, eBay, and other stores like LaptopCharge.com. Dell ridiculously overprices these things, so I didn't want to buy from them. However, I noticed that some people didn't trust third party batteries, and many people said third party batteries wear out more quickly. I also noticed that most eBay sellers didn't list a brand or part number for their batteries, which seems shady. I chose LaptopCharge.com because is a store that has been around of some time, and they sell Dr. Battery brand products. The price wasn't much higher than the best prices on eBay.
After placing my order, it arrived promptly and in good condition. Everything was packaged well inside, and the battery and AC adapter were in their own boxes. I was however unsure about whether the Dr. Battery brand meant anything. The logo only appeared on hologram stickers which were haphazardly stuck onto the battery and adapter.
The battery is a good, though not perfect fit. It takes slightly more force to engage the latches, and the thicker side sticks out a fraction of millimetre. This is totally inconsequential.
The battery charges properly and only gets very slightly warm. When it's done charging, the battery light keeps flashing occasionally, like during the topping up part of a charge. Also, if the battery is discharged to 98% or 99% and power is plugged in, Windows reports that the battery is charging but the level doesn't increase. In both of these situations, BattStat shows about 11 mW of power input, and a voltage which is well below 4.2V per cell. This seems like a very slight miscalibration of the current gauge. None of these things are a problem. (It is normal for lithium-ion batteries to require more than a few percent discharge to trigger charging.)
Just like the original battery, the replacement battery has a LED bar graph for checking battery level. It works, although the button that activates it requires more pressure and doesn't have a nice clicky feel. This is a bit of a disappointment, but certainly not a big problem.
Low battery shutdown works perfectly. The capacity decreases smoothly, and hibernation is triggered appropriately. I did not test discharge to the point of power cutoff.
During the last year, I was careful with the battery. I took it out when using my laptop on AC power for extended periods, and whenever I stored the battery, I kept it at around 40%. I still don't see any capacity degradation.
The charger looks very similar to the Dell charger, but it is bigger. This may be because it is 90W, while my Dell charger is 65W. It has a longer AC power cord, but a shorter DC cord. This is less convenient than the Dell charger. The AC cord doesn't bend where it exits the charger, which is nice, considering that I don't want to wrap the cords on the charger because of the stress that it causes.
I don't like the original Dell charger because it is noisy. It makes chaotic buzzing and beeping noises when the laptop is running and especially while the battery is charging. When in sleep mode, it produces a chirping sound as the power LED pulses. When I'm going to sleep in a quiet place, this sounds kind of like night crickets, except it's kind of annoying. The Dr. Battery charger is much quieter. I need to be closer to hear the sounds it produces, and there are no bothersome sounds in sleep mode.
Even though the Inspiron 6400 shipped with a 65W charger, it properly recognizes the new 90W charger and makes use of the additional power. With the original charger, charging slows down when the laptop is on and doing demanding tasks, and with 90W available, charging does not slow down. (BattStat can show these things.) However when charging and doing ordinary non-demanding things, the charger gets so hot that it is on the verge of causing 1st degree burns. Because of this, I wouldn't like to do constantly demanding things while charging or use the charger with a laptop which is designed to require 90W.
When I was wondering about the bar graph on the battery, I contacted Dr. Battery and LaptopCharge.com and got prompt replies. Based on this, it seems that the technical support and warranty can be trusted.