What do you think, regarding the quality, of the Tamko Hertiage 30 shingle ?

I'm not familiar with that said brand but...the "30" indicates that it is in the 30 year life span category. It should be good with an expected life in the 25 year range if you keep the roof clean from debris (moss, leaves, limbs, etc). I always recommend an architectural style verses a three tab construction. Hope that helps a little.