I was lucky enough to be given one of these as a present from work. Very easy to use - dock your ipod/iphone or itouch and within seconds you'll have a decent sounds blasting at you. I've been very impressed with the sound quality for such a small size. The bass is very strong and it has a good feel about it. Easily good enough for a room at a party or background music - it's not tinny at all.

Pros -
The sound.
No faffing, just plug and go.
Charges iphone 3gs (probably 4's but can't be 100% sure).

Cons -
With a normal Hifi you would be able to tweak the sound settings slightly. You can't really do that with these types of speakers.
Is it on or off? I can never really tell if it's on or off. I think it goes in to standby automatically when left for a bit. But there is no power light or indicator to confirm that.

If i was chosing another ipod speaker (also have a gear 4, and a kensington - neither are as good as this) I would save up and go straight back and buy another one of these.