I have noticed that using Huawei USB 3G sticks are better than the ZTE models.
Out of the box Ubuntu 9.10, the Smartbro E156C model and the Globe Tattoo E1552 models work.
I am still trying to make my Sun Broadband Huawei E1550 to work.
I have an old ZTE MF622 and it does not work out of the box.
The new Smartbro (black model ZTE MF627) also does not work out of the box.
Care to share your Huawei or ZTE experiences?