I'd heard lots about the zoo from other expats and how it is worth a visit and having now been I'd add my voice to that statement. As you'd expect and hope the animals are in fantastic enclosures which allow them the space they need to exercise and behave in a natural way. The whole zoo though is fantastically laid out and certainly makes full use of the natural flora and fauna available here.
I was a bit worried that the heat of the day might have meant that the animals would hide up but I didn't need to. The enclosures have lots of viewing points that mean you should be able to see the animals without too much difficultly. As you can hopefully also see from my photos the zoo has really cleverly designed the enclosures to ensure yours and the animals safety but also to allow you to see the animals and get great photos without any railings etc. spoiling the views. Even when it rained (and it really rained the day we went) the animals could still be seen and the weather didn't really spoil my enjoyment of the day at all.
The zoo has all the animals you'd expect to see including various monkeys, elephants, tigers, lions, rhinos, reptiles, giraffes, zebras, penguins the list is endless! Be prepared to spend the day there.
I'd definitely recommend a visit and I still have the night safari to do (another Singapore must do) and at least one further visit is in order as next year the zoo will be getting two giant pandas!