To be frank, even I am a CBSE student. CBSE is definitely enough to get you into most courses at almost all Universities across the globe. But some courses like engineering at Cambridge, and other highly completive courses at Imperial (Like computer sci, aero, medicine) becomes really hard to get into if you are in CBSE. I know many at Imperial who studied CBSE, but they are all in courses like biological science, micro biology, material science, design engineering etc. I am looking at aeronautical and mechanical and I could not even find few. Most Indians at Imperial studied A-levels or IB.
I would totally agree with everyone above, only change to IB if your sure you want to go to Imperial/Cambridge, or else it is a waste of time and money.
A small note, I feel CBSE has much more content and is harder than A-levels. I'm sure 95% in CBSE is like A*A*A at A-Levels, yet for courses with minimum A*AA they ask for 95% as conditional offers, I have no idea why, and its really sad.