I had an Evo since launch date. One of my friends and I just traded phones because he wanted an Evo and I wanted an Epic. So we did just that.
Let me just start by saying that the Epic, for me, is a much better device. I will miss HTC's Sense, and now that I don't have it, I can truly tell you that Sense makes a huge difference in how an Android phone works. It looks great, and adds functionality.
However, I have several gameloft games that I was unable to play comfortably on the Evo due to the cheap Qualcomm processor. Now, no lag at all whatsoever. Also, I love the screen. It's simply gorgeous.
The camera! Wow. HTC's Camera does not compare to the one on the Epic at all. The Epic takes much better pictures, and the video quality is unmatched by Evo. The Evo, compared to Epic, is like comparing VHS quality vs. Blu-Ray. Yeah. That big of a difference. I can't believe how much the HTC Evo camera really sucks.
I really like Samsung's skin, but I will admit that Sense is many times superior to TouchWiz.
I could go on with my list of comparisons, but I will stop and have the confidence to say this:
I think the Samsung Epic is finally a solid Android competitor to the iPhone.
Yup. I said it. The only reason I didn't have an iPhone is because it's on AT&T. I was never satisfied with the all around performance of any Android phone when compared to the iPhone until now. Samsung really did well with this. In fact, I have been doing nothing but bashing on iPhone users since I got my Epic. Everything works. I have not had a single app crash on me. The camera is just as good as the one on iPhone, if not better. The screen is awesome, not the high pixel density of iPhone, but this phone made me realize that color is what makes the difference. The screen is just as responsive as iPhone (which is a first for Android phones). the music quality is great. And the best part: my Epic is more powerful than any iPhone out there; Hummingbird really kicks everything out of the water.
My long 2 cents.
Now, I will also be buying a Galaxy Tab when it is released because of my satisfaction with Samsung. And I won't look at iPhones anymore like if I really want one. Now it's just another phone.