I was aware of the issue before I bought my SGS a bit over a month ago, so from the start I made regular MyTracks recordings. At first they were messy, with lines hovering randomly across the roads, often being seen on the wrong road, weird jumps due to lost locks, drifting badly when stopping or turning, etc. Just like many others have reported.
I spent a fair bit of time trying out a lot of different settings and 3rd party utilities. Now my unit performs same or better to any other smartphone with gps. Here are a number of my tracks:
Google Maps (enable sattelite view and zoom in to see the bike lanes I was on that google maps doesnt show as roads.)
Theres is definitely a problem with SGS and GPS but it appears to be fixable. These tracks arent flukes, i havent had a single error or loss of lock while tracking since I found settings that worked for me. And I use gps quite a lot (i dont tend to record car rides where I also use navi software, but it works fine. I'm not sure what the root of the issue is, i'm thinking maybe some sort of driver/intialization or cache problem but thats just a guess.
But I understand your position very well, its the same I was in when looking for a new phone and finding the SGS to be very attractive, except all the people on forums reporting bad gps performance. It was actually early in this thread that I debated my concerns with the folks here, and I now dare say it was actually our good and always excellently informed friend Mr Beards that made me pull the trigger and get one, instead of waiting for the Desire HD. And I still thank him for that, as I wouldnt want to trade my beloved SGS for a DesireHD now that its out
So there, to give a bit of balance to all the negative talk on forums about SGS & GPS & LAG, I felt like adding a more positive report. But the problems of both gps and lag are definately real, I just found them both to be fixable, and I havent owned a smartphone yet that didnt have some sort of issue so; as long as I can fix them I can accept that.