yep, just got mine. First thing that struck me is how fast it is. Makes my old s3 appear rather sluggish/laggy. Still working out what it can do, so may be a few weeks yet before I've fully got to grips with it. Good first, hands-on, impression though.
I've got it on O2 which does provide 4g, but I've not tried that yet. I think that's only available in certain areas at the mo, not sure. On speed I was talking about the phone's processing speed, i.e. how quickly it does things. On this point, there is a noticeable difference between the s5 and the s3.
I think the only thing I don't like, is related to this waterproofing malarkey. I'm not likely to go anywhere where I would need this facility, so to my mind it's pointless and is just trend following of the likes of Sony IMHO.
To plug the charging lead into the fone, you have to unclip a flap at the bottom (which can be quite awkward if you have fat fingers and short finger nails), and then plug your charging lead into the right hand side (there seems to be 2 types of connector but my charging lead only fits one of them)....it's just a minor 'nause' which no doubt I'll get used to over time. So, on the S5 is a little more fiddly; with the S3 of course u just plugged straight in, you could almost do it with your eyes closed.
Got me thinking though that this flap could get easily broken off if you go in ham-fisted, so maybe need to be careful with this.
sorry, meant to add, the mains charger is more or less identical to the s3 one which you probably have, although it's now white as opposed to the s3 black one. Same set up insofar as a 3 pin uk plug affair, into which plugs the (white) usb connecting lead. Then the same type of connector into the phone.