You have made a very dramatic switch there, from a very high quality film system to a consumer grade digital camera. The sensor on the Sony is probably small compared to most digital SLR cameras and that has the same effect as moving from medium format to 35mm film: a distinct loss of detail and likely also dynamic range. Add to that the fixed zoom lens - high quality, no doubt, but with a wide range of focal lengths and so probably compromised throughout - and you do not have a comparable package to your Mamiya. There are some pretty small dSLRs out there if size and weight are a problem and some fine lenses, too.
Having said that, the photographer is far more important than the gadget and the Sony is a very portable camera (with IS, so the tripod is less important) so you can safely ignore everything that I have said and just take pictures!