Picture-quality-wise, it's really quite good for its size, but for me the biggest trade-off is Standard P&S Syndrome (TM, Patent Pending): in standard focussing mode, it has a tendency to assume a wall behind a subject is the main focal point, not the subject itself. This isn't unique to the Stylus Epic from what I've seen, it's a relatively standard P&S quirk.
It can be somewhat overcome by using the spot mode, but on the Stylus Epic that's a bit of a pain as you have to press 2 tiny buttons together on the back of it (changed, thankfully, in the Stylus zoom models - at least in my Stylus 120 it's now a separate button).
Obviously, with an SLR, you have the option of focussing on whatever you want.
However, there's the old adage, "You take pictures with the camera you've got" - eg, if you have no camera because you don't want to carry around an SLR, you won't get the shot - if you have a more portable camera, such as the Stylus Epic, you'll at least get a pic - even if it isn't quite as nice as with the SLR.