T-Mobile has only rolled out the 1.8Mb version of HSDPA so far, so that's the best you'll get regardless of what the hardware can do. I'm seeing up to about 1.5Mb/s, depending on how busy the network is, on my 3.6Mb/s-capable Sierra Wireless 875.
Incidentally, if you have a PC-Card slot, the Sierra 875 can be had Cingular-branded but unlocked from the US cheaply on eBay. Mine was £78 all-in.
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Re: HSDPA Downlink Speeds
T-Mobile has only rolled out the 1.8Mb version of HSDPA so far, so that's the best you'll get regardless of what the hardware can do. I'm seeing up to about 1.5Mb/s, depending on how busy the network is, on my 3.6Mb/s-capable Sierra Wireless 875.
Incidentally, if you have a PC-Card slot, the Sierra 875 can be had Cingular-branded but unlocked from the US cheaply on eBay. Mine was £78 all-in.