The im4 is the latest incarnation from the Altec-Lansing inmotion range, and is the cheapest (mine was £62 including p&p from an online reseller).
I bought one of these to go with my apple ipod, to create a tiny portable stereo for use anywhere. The unit runs from 4 AA batteries, and comes with an adapter with 4 different socket types (3 pin UK, 2 pin European etc) so it's perfect for use while travelling.
Sound is impressive considering the size of the overall unit, and the 4 metal speakers. Bass in particular; nothing earth-shattering, but more than you would expect.
Build quality is good. The unit is made from relatively sturdy plastic, the central section is rubberised, so an ipod etc won't slip, the grilles covering the speakers are strong and protect them well, the controls (on / off and volume) are adequate.
The speakers rotate away from the central section, so they can be tilted to face upwards / angled towards you. The stereo imaging is fine, again considering the size of the unit.
Connection is made via 2 inputs - a 3.5mm stereo jack socket (cable supplied) and a 3.5mm stereo jack plug on a captive lead attached to the back of the im4. Very nice touch here - the captive lead is retractable, being pulled inside the main unit by sliding a button, vaccuum cleaner power-lead style.
Overall, a very good package to match with a personal cd player / mp3 player, and at a competitive price vs the alternatives such as the jbl on-tour.
The only caveat is I'm getting distortion, but this is down to the line-out signal from the ipod being too "loud" for the input sensitivity of the im4, something I will resolve by adding a volume control between. If you're using the headphone socket to connect to the im4, this will not be an issue.