Why buy any synthetic if this is so fantastic?
This is one of the best baselayers out there, in my opinion!
I have a couple of other Icebreaker tops, and I use them when snowboarding, cycling, climbing and walking, so basically, in all temperatures. I prefer merino wool over synthetic layers, since I find they breathe fantastically when it's hot, and have better insulation when it's cold. I find a couple of Icebreaker layers under a hardshell jacket gives me a good hillwalking combo and a perfect winter cycling combo. Even in -5c temperatures, my top half feels warm.
This layer is from Icebreaker's 'Bodyfit' line,which basically means it's fitted rather than loose. I'm 5'7 and 9st so the small Bodyfit range is just the right size for me. I find Icebreaker sizing to be pretty much spot on.
The 'no stink' reputation for Icebreaker products isn't entirely true, but significantly better than synthetics, that's for sure! A synthetic top would maybe give me a day or two of cycling or hard climbing before becoming a stink-fest; Icebreaker tops are normally double that.
Though I've not found it with this top yet, the only downside with Merino wool is that it can occasionally snag, either on rocks while climbing, thorns etc while walking, or even seemingly when put through a wash cycle at home. Snags are, thankfully, easily sewn up.
Overall, a great baselayer no matter what the temperature or activity.