Although this greenhouse was a chore to put together, it is well worth the time and patience required.  This size is ideal for the small-scale garden. The polycarbonate construction seems to draw in light!   I am able to put in three shelf units which hold nine flats each!  It still has space for large pots and I am currently using it to harden-off transplants.  It will be a great season-extender as I plan to use it to grow fall cool-season crops and take in some tomato and pepper plants from the garden, as I live in zone 5 this will be a great asset.  I did add the automatic vent opener and feel it's an important accessory for a greenhouse. 

Pros: Durable, great engineering, high quality product.
Cons: None.