I have a lot of problems with my epic. I owned it since September of last year and it was great for about the 1st month. Now these might be just complaints or legitimate problems...I'm not sure.
Initially with the stock 2.1, battery life was horrible. I would go maybe 3/4 of a work day and it would need to be charged. Honestly I didn't have too much of a problem with that, but it kind of sucks when I'm out and about on a weekend and my phone is about to die.
2nd is I had so much trouble with hanging up or making phone calls at time. It would lag like the cpu is overloaded.
3rd the problem that bothered me the most is mp3 files. It would come up with...this player does not support these files. It would happen randomly. This became an issue when I used my phone as an alarm with an mp3 as my alarm. My alarm wouldn't go off since it can't play the mp3. This includes my ringtones, so I would just get silent. This would work after a reboot, but I would have to reboot twice a day for my simple mp3s to work.
So I decided to go with the rooting. Phone became super fast, battery life would exceed a day, and all was merry in the rooting world.
A month after that, I'm having problems again. The mp3 issue came up once more, GPS is even more horrible than it was before, and occassinally my phone would force close google framework. Now I can't text or make calls, and sometimes it crashes bad enough where I can't even use my phone whatsoever. I'll just have to re-image my phone and all is good for a short amount of time. Couple other people I know have the same issues.
So here I am looking for answers since I thought rooting would fix my issues.
I am so with you on this one. I purchased my Epic 4G Aug 2011 went through 3 phones in 3 weeks and it had still been a total nightmare and I was ready to leave and go to Verizon and throw my phone against the wall.
GB update came. My phone was locked in a constant reboot cycle so you can imagine how angry I was at that point. I did notice that if I took out my SD card it would stop the cycle. I need the files/apps on my SD Card so I finally did a factory reset without my SD card installed. WOW! I have a nicely stable phone that runs faster and fixed about 99% of my previous problems.
Here are two apps that I discovered that I think are a must have. The first one I found just before the update and I will always use this app. It's called PowerMax if you haven't heard of it yet. It's in the market here:
https://market.android.com/details?...251bGwsMSwxLDEsImNvbS52b2x0dXAucG93ZXJtYXgiXQ..
The second I accidently found this new app called Airdroid which can be found here:
https://market.android.com/details?...t=W251bGwsMSwyLDEsImNvbS5zYW5kLmFpcmRyb2lkIl0.
PowerMax since my testing has been the best by far the top battery saver. There is a 7 day free full trial. After that it has ads if you decide not to purchase it. Everyone who hasn't tried it should seriously give it the 7 day trial at least. It has worked flawlessly on Froyo and even seems better on GB.
Airdroid is in my opinion THE top app for accessing your phone through the Mac and PC. I have been testing it on the Mac since my PC is dead and no need for physical cable. Just the same network for your phone's wifi and you computer. You access your phone's files through the web browser and it is awesome. You can even back up system files. I'm not sure if its all of them but there are quite a few system files I did back up to my Mac. Its kind of like doing a nandroid backup on non rooted phones which is where I'm at. I backed up everything on my Mac and it runs pretty quick. Definitely give this one a shot if you have problems with your computer recognizing your phone.
Hope this helps others as much as its helped me. These again are must have apps for my phone. Juice defender has nothing on PowerMax and I haven't found a back up app that works great on the Mac than Airdroid.
Jim
One other thing since the GB update. On Froyo I took advantage of the 15 minute return policy and tried SPB Shell 3D and it crashed constantly, force closed, froze up and usually within 5 minutes so I returned it quickly. When GB came out I tried it again. I emailed SPB and they said they would refund after 15 minutes if I really was unhappy with the app so I tried it again. I've been using it for about 5 days now and with the exception of a couple of reloading when you do a lot of multitasking or stay in an app for a long time which is taxing on the memory it has been running great which totally surprised me. My birthday was the day before the GB update so my niece purchased it for me. Sure, its an expensive app for a launcher but I just love the eyecandy and I can always switch back and forth between that an my other favorite launcherl, Go Launcher EX and being that its a free app I figure I'm paying about $7.50 for each one.
There is one thing I have noticed with the GB update though. There seems to be some memory leaks which I hope they will fix with an update. During the day I notice about every 2-4 hours my cache builds up anywhere from 1-10 megs at times depending on what I'm doing on my phone. I use the App 2 SD widget by Sam Lu which shows cache and free internal memory so I just use that to quickly wipe out the excess memory leaks but it would be nice if I didn't have to do that. Outside of that I feel like I have a brand new phone but I still don't forgive Sprint for their lack of good customer support.
Though I must say, they have to be working hard on it. For a bit there seemed to be a new release every two weeks trying to iron out the kinks. I guess some of those kinks are proving to be quite formidable. 
