Hi soonkhoo!
It's good to hear that someone is interested in this extraorginary product!
In general there are much more pros for using Opera than cons - ease of use, features, speed (page loading as well as files downloads), built-in mail client and ICQ-compatible messanger, standarts compatibility, etc.
It depends on what exactly do you want to know.
I personally use Opera for more than a year already and can say that it leaves IE and NN far behind in most cases. Main exceptions are non-standart DHTML scripting and local encodings.
If you want to develop sites for Opera the main clue is to follow the standarts strictly (as for NN, actually), and you won't have problems.
There is a good specifications list at
they finally did it.
Welcome to the Opera club!
Andrew | starway@mail.com