im using for my internet connection the huawei e3531 umts stick and it works perfectly fine. Because i use more than one device i bought the TP-Link Wireless Router TL-MR3020. i put my umts stick in there and it lets me connect thorugh wlan to the internet and that also works great, but:
my destop pc uses the Edimax EW-7811Un for wlan and there is the problem.
can be used as mobile broadband connection or used with gammu/wammu to send/receive SMS messages and phone call's. there is a problem with USB charging if the phone is totally empty (it will only charge with the original charger)
I have the UMTS Stick Huawei E160 with a prepaid SIM card from tchibo/O2 in Germany. The prepaid SIM allows daily flat-rates at a reasonable price however I need to send and receive a SMS (short message service) in order to book the daily flat-rate.