If you encounter any problems please describe it in this thread.

Thanks a lot!
Waiting for C# upgrade!

PS
and dont forget to import(add reference) System.Numerics :)

Can you please describe the most significant changes in this compiler compared to previous one?

well.. I'm very glad to find that an additon "system("pause")" in the last line won't lead to WA still. (Otherwise we may encounter lots of WAs if there's rejudge...)
However, I noticed that there's a slight difference in the memory usage indicator. A+B Problem, for instance, previously they're 121KB for both C/C++. They are actually 104/188KB now. It's not a very critical problem after all :)

I'm just a bit afraid that we may have to change a little bit of our "code style" to fit with the new compiler... Then go for it~

Bytewise reading now works slower than scanf.
Thats the first thing I've noticed.