Out of curiosity, who was giving the lens a bad review? I had a 300mm f/4.5 AIS before switching to the 300mm f/2.8 ED-IF AIS a number of years ago. The f/4.5 is a very sharp lens, and very solid and well made, though like all lenses of its focal length which do not have low disperson glass, they are prone to some color fringing. It is not bad at all with the f/4.5, however and only noticeable with very large magnifications. You will be very happy with it, I was! I just wanted something I could close down one stop to f/4 and have even shallower depth of field than you could with the f/4.5 and still be razor sharp.
To show you how well it is made, I used to focus mine all the way to its minimum focus, set it on the table and would watch the weight of the internal sleeve turn the focusing ring at a very smooth and deliberate rate. It is smooth as butter. It was like watching a clock. Their lenses are NOT made to that standard any more, regardless of price. Even though the entire inner sleeve with all the elements moves, you can still focus it with one finger except on cold days when it is a little stiffer.