I've actually been using my 550D/T2i for work and making money with it. So I have no idea what the heck Albert is talking about. He just sounds like a bitter person unhappy with everything.
There are issues with the 550D, most certainly. But you work around them and you get the job done. I've used the 50mm 1.8 and created both video and stills that sell. I've used the Sigma 70-300mm (which I'm sure Albert would say sucks) at F5 and even F12 and created images and video that sell. Heck, I've used the kit lens with the IS and sold video to my local television stations for hundreds of dollars.
The only thing that sucks is the attitude that everything sucks.
Yup... It sucks that you can earn some cash with so cheap equipment doesn't it? I am glad for you. But, if you want to have the best results (perfect), then there is no limit in money you can spend to get there. That was my main point. And YES - 550D is excellent camera for money it costs as well that Tamron SPXRDiLD Aspherical (IF)... But, there can be found better and worse depending on your luck as well money you would have to spend...