I am using Idea Netsetter usb modem for browsing the internet for past 3 weeks or so. I must say that contrary to most of the negative reviews given here, the modem works very well with my computer. However there is a catch; unlike most users I am not using an Idea SIM card. This modem(Huawei E1550), has been bought "unlocked" on ebay.
I have used Tata Docomo, Aircel and Vodafone GPRS/EDGE services successfully on the modem and on both Windows and Linux(Ubuntu 10.10), and for a 2.5G network, the speed is very satisfactory.
Device: Huawei E1550
SIM card: Tata Docomo
Tariff plan: Rs.48(1GB download/upload with 30 days validity)
Operating system: Windows XP SP3 and Ubuntu 10.10
Connection type: EDGE/GPRS
Speed: 110-240 kbps download: 60-100kbps upload
The screenshot provided is for Tata Docomo GPRS. I used Firefox 4.0 in Ubuntu 10.10 for this test. Please note that internet connection speed is dependent on signal strength. We have very good signal for most mobile operators in my area, so connection speed stays decent most of the times.