What problems? Have both and the charge has given me more grief then my nexus. I am on my third charge and on my first nexus. I still think the charge was the best device out at the time I bought it and a good phone. Not sure if the fp1 update fixed all the issues. Spend the extra money and get the nexus. For sure you will get the jelly bean update and possibly key lime pie.
I had the Galaxy Nexus LTE/CDMA version since day 1. So after 3 1/2 months, I gave up on it and sold it a couple of days ago.
Great device. Loved the screen. Loved ICS but Samsung has horrible, and I mean horrible antenna design problems on many of their CDMA phones, including the galaxy nexus.
Final straw was when my friend's Droid Razr was able to get 2-3 bars of LTE signal at my house and my Verizon LTE iPad gets 3 bars at my house also.
But my Galaxy Nexus never gets LTE signal and CDMA signal is 2-3.
At work, I get a 30-40% no signal on my Galaxy Nexus, which is ridiculous. I mean no CDMA, no LTE.
So if unless you live in a very strong Verizon area (I am in Orlando); if you live in a strong area, than the Nexus is great. But if it's a "fringe" area, you will be kicking yourself because even the leaked 4.03/4.04/05 software update do not improve the antenna.
Getting back to the original question. I wouldn't waste your upgrade on the Droid Charge even if free. You can find them on craiglist for $150 these days no contract in good condition.
Even the Galaxy Nexus goes from $350-450 on craigslist perfect condition. This sure beats spending $299 on contract for the Gnex (you can get it a little cheaper on Amazon (for $229 for upgrades). Amazon has them for $99 of NEW customers.
There are other phones coming out in the next couple of months. So if you need a new phone now, get it used. Save your upgrade.