Hi...I'm a new member also, having lurked and read postings for the past couple of weeks. I can appreciate what you're going through, as I was diagnosed two weeks ago, T1C, Gleason 4 +3, 2 of 16 cores. My wife and I have pretty much spent 24x7 on the internet as well as reading Walsh's book and going to various docs.
Re proton beam, I have had the same experience as you as the claims are for "lower side effects". After talking with a radiation oncologist friend, as well as the radiation doc to whom I was referred by my urologist the answer I've gotten is: "the lower side effects were true even 5-6 years ago, but with the improvements in other types of radiology and surgery, that is probably not true today". In the absence of any clinical trials or current proof, and not withstanding the anecdotal evidence provided by www.protonbob.com, I have personally come to the conclusion that proton beam is no better or worse than the other options...that may or may not be factual, but that's where I am so I have eliminated proton therapy from my list of options.
FYI, since you are concerned about side effects, there is an excellent ariticle in the New England Journal of Medicine, www.nejm.com, March 20, 2008, entitled "Quality of Life and Satisfaction with Outcome among Prostate-Cancer Survivors". It costs $10 if you are not a NEJM subscriber, but it is well worth it to have up to date info on this important issue.
Finally, I still have not made a final decision...but, I'm down to 2: brachytherapy or robotic surgery. I have found docs who have done over 500 of each procedure respectively and I'm confident that whichever one I decide on will do it well. Frankly, I'm leaning toward the surgery...I have always told my daughter that OPTIONS are important in life. The fact is that if, God forbid, the cancer is not completely cured by the first procedure, there are more options later if you have surgery first rather than radiation. Anway, I'm still mulling it over...
Good luck as you work your way through this.