I have the HUAWEI mobile E220.
Using the drivers that came with my T-mobile webnwalk pack it worked first time in leopard.
You can get the drivers from my dot mac space
http://homepage.mac.com/timhaigh/E220_Drivers.zip
Once installed you can use the HuaweiDataCardApp to set your APN.
I don't require anyother 3rd party software to make the conneciton.
I went to SystemPreferences-->Network-->Location -->Edit Locations
click the +
I added HSDPA as my location name.
Then I chose add configuration
I called it 'T-Mobile'
I used *99# as the telephone number
my provider does not require me to use a username and password so I left that blank.
I checked 'show modem status in menubar'
Then click Advanced.
click the modem tab
Vendor:Other
Model: Huawi Mobile Connect
I have enabled error correction checked
Dial mode 'ignore dial when dialing'
Then click the PPP tab
Settings:configuration
uncheck 'send PPP echopackets'
Then click ok
then Apply
Now to engage the connection I plug in the usb modem wait for the green or blue light to flash.
I goto the menubar modem icon and choose Connect HuawaiMobile
This works.
Now to monitor my modem signal, usage etc I use cheetahwatch
http://m.ac.nz/cheetahwatch/
Good luck