I bought one of these a couple of weeks ago, to use on my commute to london.

The Good:

• Uber convienient have BB on the move
• Signal on the train is good without to much drop out.
• You can plug in a 4gb mcro sd card and turn it into a memory stick
• In a good signal area the downloads are fast 170kbps
  

The Bad:

This is a relatively expensive way to roam the WWW at 15 quid per GB but it only costs 39.99 to buy and you only pay for what you use unlike the pay montly alternatives. Perfect for me as I will only use it for small periods.

The Ugly:
The vodafone software that installs when you plug the device in to your Pc/Laptop is possibly one of worst programs I have had the misfortune to encounter in a long time.
If you plan to use this device whilst stationery and in a good signal area you will not have any problems. If you use it on a train / in a car then expect constant pop-ups that cannot be minimized.

The unecessary:
Adult Content Blocking is on by default, included is Skype.com ???
WTF Vodafone since when do Skype serve adult content.... Hmm they do however offer internet telephony, I wonder if that could be the real reason.
Which ever knob jockey at vodafone thought up this trick should be shot. It just annoys paying customers who can download skype the moment they are connected via WiFi, seriously misjudged move by Vodafone.

Update: Tip
You don't have to use the crappy vodafone software, after you have installed it open network connections and right click on the Vodafone connection and select connect. It is also possible to prevent the vodafone software from launching when you plug your dongle in, just go to the options in the app. The only thing you lose is the usage meter.