Has anyone been there as a tourist, if so what to see etc? I am having fours days there and finding it a bit hard to fill in my itinerary. I also plan a day trip to Lubeck.

Yes, been there, there really isn't much to see, the sights in the city will keep you busy for a day at best. You can take a tour of Rathaus. Four days is too long to spend in Hamburg, IMO.

Depends on your interests (and the time of year, by the way).

Besides the obvious (lots of museums, harbor boat tours, the famous zoo, several Musical theaters, nightlife on Reeperbahn/St Pauli district):

Miniature Wonderland (forget everything you ever heard about "toy trains")
http://www.miniatur-wunderland.com/

Ballin Stadt (the emigration museum/experience)
www.ballinstadt.de (click on Union Jack to switch to English)

Fish Market
an early morning experience


Day Trips:

Lübeck is a great idea, but also:

Lüneburg
http://www.lueneburg.de/en/desktopde...aspx/tabid-358

Friedrichstadt (the "Dutch town")
http://www.friedrichstadt.de/
Only in German, though. But if you click thru the pages or do a Google picture search you will get an idea.

Altes Land (around Stade and Jork)
esp. during cherry/apple bloom

I am sure hsv will have some suggestions for you. I found Hamburg to be a very interesting, vibrant city and enjoyed my stays there. Like Cowboy said, it depends on your interests.

I enjoyed a cruise on the Außenalster lake and the little canals. Also, a walk through the residential areas in the North (Eppendorf, Harvestehude) was quite interesting (Art Nouveau houses, the small church St. Johannis). Churches worth to see are St. Michael, St. Jakobi. Expressionist architecture (Chile house) is interesting. The art museum Kunsthaus is very good. Check if there's an exhibit in the Bucerius Kunstforum. And then there is the Speicherstadt (the warehouse district).

I second the recommendation of Lübeck for a day trip.

Thanks to the two helpful replies of Ingo and Cowboy above, it has made me keen to visit there now and to take in some of your suggestions. I know there will be plenty for me to experience but it's just that my German is very limited so was not sure which of the areas were the most interesting. I can see I will be fully occupied now, thanks again.