I would either go for the Thunderbolt or wait for something else. There is nothing too exciting about the Droid Charge except the fact that it is 4G. The $300 price tag is outrageous, especially for a non dual core phone, and Samsung has a very bad history of updating it's Android phones (the Facsinate/Galaxy S JUST got Android 2.2 Froyo). Try a TB and come the UI to the Fascinate, I guarantee you'll like Sense better then that schlop Samsung has come up with. And while the battery life is horrendous on the TB, I suspect this will be a common problem with all 4G phones and the positives outweigh the negatives.
The TB is also unlocked, meaning that ROMs can be flashed on it with ease. You might not care about this feature, but I'll tell you the number one reason that Droid 1 users haven't upgraded yet is because we are running these beautiful new roms that have brought our phones up to speed and kept us from getting bored.
Also, check out Motorola phones, like the Droid 2 and Droid X. Even if you don't want a non 4g phone, see if you prefer MotoBlur (or if you can't bare it, it's a love it or hate it thing). You may want to wait for the Droid Bionic, Droid x2, whatever the heck they have coming out. These phones are going to be dual-core and will be 4g. Although these phones are locked, making flashing difficult, Moto puts out quality products, as seen with the number of Droid 1 users still out there.
Also, check out the iPhone, you may like it.
Good luck and let us know what you decide on!