I'm with Sprint, currently using the Galaxy S. I think it's the precursor phone to this Epic you're considering. My upgrade eligibility date is in April.

For the most part, I've liked the Galaxy and am likely to upgrade to the Epic. Battery life isn't the best, but since new batteries for this phone are only about $3 (incl. shipping), I just keep a couple extras in my bag.

I love 4G when I'm in an urban area where the signal is strong. I tether often and can absolutely tell the difference - it's a near-broadband experience. If a hotel only has spotty Wifi, I just tether and don't bother with the Wifi. (Still prefer a wired connection, of course.)

If I'm in an area where the 4G is weaker, I disable it and use 3G. The Galaxy seems to get confused when it's receiving and dropping 4G often. And as others have pointed out, battery drain...

Starting to feel like the Galaxy is a little underpowered but I figure that's normal. Apps are getting more resource-intensive and, well, I need to upgrade my phone. A couple friends have the newer Epics and love them.

I'm not as high on the navigation as some of you guys are - I still carry a Garmin for that. It doesn't happen often, but it seems to happen at inopportune times: my Galaxy will lose the cellular data connection in the middle of a trip. The phone is good in a pinch...if I'm somewhere without the Garmin...but the online reviews I've seen that say "better than any dedicated GPS unit" are very hard to believe for me.

I've been with Sprint forever and have a flat 28% discount off of my base rate. I too have noticed that the 28% seems to apply to less and less these days. I got the 28% when I signed up...it was the original launch of PCS and a sales rep showed up at some conference or telecommunications event - I forget where. He said "you'll have the discount as long as you stay with Sprint", so I haven't changed. But I always wonder if I could walk into a Verizon store, show them my bill, and have them produce some sort of "discount" of their own. Everybody I know gets discounts from their wireless carrier so I assume it's pretty common. AT&T sends me 18% "corporate discount" offers all the time but there's no way I would go with them.