According to
Henning Gajek's blog entry the Blau stick is a
XSStick®W12 from 4G Systems, which supports UMTS2100 only.
€ 99 is a real rip-off if you consider that brandnew Huawei E180 dongles (feature HSDPA 7.2 MBit/s, HSUPA 5.76 MBit/s, UMTS900/2100, microSD-reader, voice telephony) are sold in the Vodafone version
for € 60 at eBay.de (called "Vodafone K3715", unlocked and easily unbrandable by a simple
firmware update from Huawei).
Beyond that you should be aware, that blau uses the eplus network, which is total crap, as it neither supports HSDPA nor EDGE and further is overloaded in many many places. Especially during peak hours you often cannot even establish a data connection on the eplus network and if it occassionally succeeds you have modem speeds and I'm not talking about those "fast" 56KBit/s-modems. Also eplus has configured a restrictive overload protection on a lot of NodeB's which causes subscribers to be handed over to GSM as soon as a connection (no matter if voice or data) has been established. So there's really no use of a UMTS-device on the eplus network.
By the way, Henning Gajek wrote that he tried to post the above linked blog entry through the Blau stick, as he was writing the article while unboxing it, but he resigend and switched to his ADSL-connection, since data rates were terrible.
So folks better keep your hands off eplus and all the MVNO's that use their network, as you will get way better service for the same price from Tchibo, respectively O2.