My first Icebreaker has about 18 months of all kinds of outdoor activity on it now.  It is holding up very well, stays warm when wet, dries quickly and never seems to stink.  The zip neck is good for getting a little temperature control.  This has become my go to first layer for a really wide temperature range.  I really like my smart wool stuff but I give a slight nod to Icebreaker.  At the sale price of under fifty including shipping it is a steal. I would buy several more if I could justify them.

As noted, these do run small.  I wear a large in most everything and the XL is a good snug fit.  Not UA compression snug but a nice, stay where it belongs snug. I also have long arms and the one size up gives me nice full length protection.