Personally, I have been there 3 times in the last 5 yrs. Twice under the old management and once within the last year under the new. Before you literally needed rain shoes to come out dry, the employee's were horrible (the ones I came into contact with) who knew very little while giving "expert advice", their prices were through the roof, and quantity doesn't always mean quality.
BUT, in my last visit I was surprised that they cleaned the place up. They made it much smaller getting rid of the majority of freshwater fish and had employee's who knew more than the old employee's. Also, I was asked three different times if I needed help and talked to the manager and another employee for about 20 min about fish stuff.
If I were buying something I would go to one of our sponsors vs. them because, lets face it, with this economy my loyalties are to the ol'mighty dollar and who can give be the greatest deal.
There's many other reasons why people don't like them but these are from my experiences, and as I said their store has changed a lot for the better in my last visit.