You can get a very good looking shirt off your printer. You just have to have good artwork.
I went to a dozzen silk screeners here in the Dallas area and looked at their samples. I was very unimpressed with what I saw (on colored shirts). And, I was able to print on white shirts at least as well as they were with my Cannon BJC-5000 printer and a hot iron. But, I make a living by selling my artwork.
Also, with a silk screener you'll have to pay extra for burning your screens, color seperations and photo work. One screen per color. 4 colors for most designs on white shirts (black, red, yellow and blue, you can get other colors by mixing these). You might be looking at $200.00 before you pront the first shirt! If your planning on printing 80 or 100 shirts, then silk screening is worth it. But, if your just want to print 4 or 5 shirts to throw to the crowd at a show, do it at home on your printer.