Hard to believe that Samsung is so dumb that they could not have done this fix at factory level or it may be a conscious decision not to have the gps signal powerful enough.
My i9003 was not having any gps locking issue but earlier it worked only outdoors & would lock in 15-20 sec with 10mt-50mt accuracy.
I took kitchen foil & folded it few times to make 1cm area of antenna cover with it...................................cant believe the gps NOW works indoors & locks in 10-15 sec with 7-8 satellites in view. I tested indoors with 1 floor above & 2 floor above. In a multi story building it locks perfectly in a drawing room, in small rooms you take it near windows & it locks perfectly............................amazing.
Outdoors it locks instantly within 2-3 sec under clear sky with constant 5mt accuracy to 11-12 satellites.
So I took the gps on a 800kms drive & after extensively using it now I am confident that I can fully depend on it, one downside is that gps using sucks battery fast so gps constant use need a car charger which now I need to buy.
Samsung route 66 shows navigation perfectly with 5mt inaccuracy, on the way I could locate restaurants, petrol pumps etc well in advance in a new cities which otherwise I didn't have any clue about.
Here are few screenshot I took at various location as proof, now I constantly get 30-40SNR in gps test with constant 5mt accuracy.
This post has images showing how pressing that area with tape helps the gps signal wire underneath.
http://xdaforums.com/showpost.php?p=13190989&postcount=4