The carbon dioxide (CO2), water (H2O), and sunlight become new energy (stored in a sugar molecule called glucose, C6H12O6) and oxygen (O2). The original elements that make up carbon dioxide and water are never lost or destroyed during the process.
I would most likely react in a positive way. Photosysntesis is pretty cool! I would probably say woow! or gasp loudly. However reactions to vary based on the individual i know many people who find the color green disgusting. For this reason they would probably say "ew" or "urgh" and be fairly negative.
