I use the Raynox DCR-250 with my 50mm f1.8.
Pretty satisfied with the results it can produce.
You can go to my thread to have a look.
Or take a look at Troy Parry's (TroyP) macro, his macro shots are amazing.
I'm still learning to get to his standard.
He's using the 50mm + Raynox combination too.
Although buying online is cheaper, but if got problems with the items will be quite leh cheh.
Need to contact the company for refund or 1-to-1 exchange, then need to ship back the item.
Some buyers prefer to look and inspect at the item before buying.
I am one of them.