@Paul : as mentioned, seeeduino clones (like my mega) come with a switch that enables you to toggle between autoreset and manual reset. I guess this is a cheap but nice feature (even a jumper would do) that all arduinos should have, given that communications seem so much easier with this option.
Anyone speak italian ? 
Thanks for the hints on the open/close and reset. The open/close : I think I would prefer to open/close since I intend to use an xbee (or some other wireless system) to get readings only every 15 minutes or so. Unless I am overlooking anything ?