It gets the flash off camera whilst maintaining full ETTL, though I rarely use ETTL it is a nice feature to have when set-up speed is an issue. This is why I bought it and it meets my expectations, though canon should really update it...
Although a line of sight must be maintained with the strobes a bounced signal also works so this is rarely an issue (and could be solved with radio poppers). It would be better if the unit ran off AA batteries for convenience. My main gripes are the lack of second curtain sync and when using the ST-E2 as a focus assist only the camera still thinks a strobe is attached and so under exposes the shot.
All in all though I knew what I was buying and am pleased with the product - I'll definatley be in line for the ST-E3 though if it ever comes out. In my opinion the ST-E3 needs to run on AA batteries (or even AAA), have 2nd curtain sync, operate 3 groups, be smaller and more robust and most importantly, let the camera know when no strobe is attached!