I have a few pieces of various weight Icebreaker, and I strongly reccomend it over other (usually cheaper) wool pieces. The lighter weight superfine fabrics are unbelievably comfortable. My 150 GT (GT=designed with a more breathable weave in some places) tee I find great on its own down to about 13 or 14 degrees celcius, and is still comfortable up to about 32C-which is about when I start sweating up a cotton or other "cool-fabriced" t-shirt anyway. The other weight garments I also find to have a great temp range, and are warmer than the equivalent weight synthetic thermals, aswell as some cheaper wool thermals I have (Wilderness Wear-made in Aus). They are also incredibly fashionable, with a huge range if you are into that sort of thing. If you have any problems they are great with returns.
Hope this helps,