Walk Behind Lawn Mowers

I just purchased a Husqvarna rear drive 22" self propelled mower from Lowes on Saturday 10/13/12. As I have seen others on this site post, when I got it home and set it up, it starts fine, runs great, cuts well and picks up the grass packing the grass catcher great. The problem is it is not very well self propelled. More propell assist if anything. On slight grades or in thick grass, not tall, it will not pull without me having to push it. My old Lawnboy which just died and could not get parts for had no problem like this. It ran up large grades and through thick grass with ease. Is the Husqvarna mowers being great tools a myth? As stated above it seems there have been many complaints about the self propelled units not pulling very well at all. Should I take it back and go back to Lawnboy? All the hype states that Husqvarna are great tools. Have I been mislead?