I currently have the Epic, I have had it for almost 30 days, and I have quite enjoyed the phone. But, over the past couple of days I have seriously been considering switching to the Evo. I have already had to replace the Epic 8 days after first getting it, cuz the screen was getting too loose on top of the pull out keyboard. It was fine at first, then started doing that, that's why I returned it for a new one. This one has been fine since I got it, but the keyboard and screen have been having the same issue again. I realize that over time the keyboard and screen will have a little bit of movement when you tap on it, but not within a month. I have OCD, and the screen movement REALLY bothers me, and I am constantly having to check it to see how much the screen has starting moving as soon as I wake up. It has gradually gotten worse since I got it. I don't mind Touchwiz, or anything else about the phone. The SAMOLED screen is really nice, but I think that my decision to choose a phone just because of a screen and keyboard was stupid on my part. I love having a physical keyboard, because on my Hero I was always fat fingering the keys, and screwing up my spelling. I love swype on the EPic, but I know I can get it on the Evo too.
Another huge problem I have been having on the Epic is the fact that it will NOT register on my PC. I have all of the correct drivers installed, but nothing works, so I have not been able to root it. I know that I can root the Evo much easier, I rooted my Hero, the long way, so it shouldn't be too hard on the Evo for me. The fact that the Epic does not have Froyo bothers me as well. On my Hero I was stuck on 1.5 until I rooted it and put a 2.1 ROM on it, and even though Samsung has said Froyo will be out by the end of November, I don't think I want to chance spending this much on a phone, just to have to wait until next year to get Froyo. I generally like to get a new phone every 6-9 months, as I get bored after awhile, and with the Evo being less expensive, I don't think I would mind getting a new phone in 6-9 months considering I'll have paid MUCH less on the Evo than what I am currently supposed to pay on the Epic. The fact that the Epic also can not play flash videos is extremely frustrating as well, and the youtube app sucks. Every video is grainy and pixelated. Samsung may have their media hub, but I do not ever use it, despite people buying the Epic today being given a $50 credit for use in the media hub.
The kickstand is also a big pro for me as well, as I am getting tired of holding my phone to watch the DVD's I have put on my SD card. As far as battery life, I have heard that both phones suck in that regard, and my Epic is needing to be charged 2-3 times a day, as I am a constantly sending texts, emails, checking facebook, and using a handful of apps throughout the day to catch up on news, or whatever the app I'm using does. I enjoyed sense on my Hero, and kinda miss being able to scroll through all of my apps quickly, but that is not a huge deal for me.
I originally thought that the physical keyboard was awesome because I would have the whole screen to see while typing, unlike on the Evo, which when typing the screen is taken up by the on screen keyboard. That was something that bothered me on my Hero, but I think I'll have to get over it, because it really is not that huge of a deal.
The Epic does feel pretty light, but I do enjoy that the phone has rounded edges, and is not too huge in my pocket. The Evo does seem like it would be a huge bulge in my pocket, but that isn't really a breaking point for me either.
I have never had a samsung phone, but have read many horror stories about samsung abandoning a phone for their next big phone coming out. I realize that the galaxy s series probably wont have much of a problem in that area, but with the gps issues, hotspot speeds, and 4g connecting issues that have not been fully addressed, I think that the Evo has much more support than the Epic does currently. Because I rarely am able to get even 1 bar of 4g service, and I'm on the outskirts of our 4g area, but my buddy with his Evo gets a couple bars constantly that doesn't drop off after 30 seconds.
All in all, both phones have their pro's, and both phones have their con's. I think that it all comes down to personal preference, and what you will be using the phone for. I realize that my switch to the Evo may make me miss how crisp my video's and pictures are that I take, and that the screen may not be as good in the sun, but that is stuff I'm willing to compromise on for a more solidly built phone that I wont have to constantly check the keyboard to see how much wiggling room it has today. I have 2 days left on my 30 days, and I really hope that I do not regret me decision to switch to the Evo, but it does seem that the Evo has a bigger Dev base than the Epic does currently. Though, the Evo has also been out longer. We shall see how this all turns out!