Been loads of times and the best for most action is the hide right in the middle overlooking the reed beds.
The spring hide had a hornest nest in during the summer and was a feature in its own right
Best moment I had was when i sat on the bench overlooking the cress beds and an Otter came out of the water, had a wash on the concrete apron and then dropped back in the water.
Yep you guessed it, no camera, had just gone for a stroll in my lunchtime from work
Keep your eyes open in the trees, quite often Deer to be seen and some surprisingly large Trout given the size of the stream
There is a board in the window of the teaching hut that gives the latest sightings, its next to the porta loos and honesty box, sometimes there are leaflets available too
Enjoy your visit and if you want another pleasant place in the vicinity you could try Paxton Pits near St Neots or Fen Drayton lakes which is north of Cambridge just off the A14