I've just started with 3 mobile recently, I get 5 solid bars of reception on the ZTE MF 112 all the time, however speed is very sensitive to dongle location. A slight twist to the vertical axis or slight lean can make a huge difference to speed.
I recently got my highest speedtest @ 6.98 down and 1.61 up with a 75 ms ping.
http://www.speedtest.net/result/1235463678.png
I'm going to get the Huawei E367 very soon and hope the multiple antenna and new chipset provide a more stable speed due to the HSPA+ technology.
I'm definitely replacing my land line with 3g mobile when my line contract expires. I'll be working towards a 3g router set up with additional antenna if needed.
I'm also presuming that 3 are going to update their network this year to HSPA+ because they've just released the new dongle and the forthcoming Samsung Galaxy S2 also supports HSPA+.