I also have a 620 and have had no problems with both wi-fi upload at home and bluetooth upload via my phone. I didn't have to do anything special to get the wi-fi to connect on the first try. I have had the odd instance of the run not uploading and having to turn the watch off and on again but that happens rarely, otherwise it's been fine.
Depends on what features you need out of the watch really - I managed to get a second hand 620 recently for a little over £100 and have been very happy with it so far - had a few blips with the watch not mapping the correct route initially but that has settled down now. It's very quick to find a GPS signal, has a proper charging cradle and you can upload your runs over wi-fi which I find very handy. You just get home from your run and it automatically uploads, no need to have a computer on.
I was using the 410 before that (again bought second hand) but it was taking too long to get a GPS signal, the charging cradle was very unreliable and it would also be off course quite often as well.
+1 for vaseline - works perfectly for me. Both for the niplybobs and the happy sack -for some weird reason I get chafing down south depending on what shorts I wear so always blob a bit on down there for good measure.
I've just bought a second hand Garmin 620 having been using the 610 for the last 18 months. One of my main gripes with my 610 was the length of time it took to get a GPS signal and the inaccuracy of it in built up areas - I run through the centre of Glasgow quite regularly - it would be fine if you could get an open area to get a steady signal but it would be reliably bad if you tried to get a signal close to any buildings, typically what I would have to do is run down to the river and wait 2-3 minutes to get a signal and then start every run from there.
I had hoped the 620 would have been better - I have completed 2 runs with it so far and both have had dodgy GPS traces - It is much quicker at getting a GPS signal, however that's not much good if the accuracy is still unreliable. In both runs I was sticking to either the footpath or on a marked trail - both runs are ones that I have completed using the old watch so I can clearly see the drift between the old watch and the new watch - in various places I'm running through buildings or along private gardens and sometimes even walking on water!
The watch is running the version of the GPS firmware (3.3) after the update that was released to fix GPS issues last year I believe. I've also set it to record at 1 second intervals rather than using smart recording.
Just wondering if others have experienced similar issues, any tips? Do you have to do anything in particular to set it up for first use - leave it in clear line of sight for 1/2 an hour or something?
It is rather frustrating - just glad I wasn't going for it on any of the runs as I've missed lots of Strava segments with the dodgy GPS