I LOVE this unit. For the price this thing is amazing. I use it when I play about twice a week.
There were so many reviews that it was hard to use with glasses, or did not lock to the pin quickly. I have found neither of these to be the case. I wear glasses and have no problem seeing through the viewfinder. The unit easily and quickly locks onto the pin from over 200 yards away. My buddy was using his Bushnell right next to me, we both got the same reading, and his did not have the slope calculation so he was constantly asking me to give him the reading.
This unit is great, I and I highly recommend it.