First of all, thanks to everyone who posted a reply to my question about suggestions for a short PA in the spring. I am now beginnig to research and gather my gear and have a few questions. I was wondering if anyone could explain the advantages or disadvantages of a down bag versus a synthetic. Is there much of a difference in weight? Also, if I plan to do the majority of my hiking in the spring, summer, fall months, should I be ok with a three-seaon bag? I was thinking that a bag with a low temperature rating would be hot in the summer months. Thanks again in advance for help.