I used to be an anti-GLT extremist, but over time I've just come to consider it very very odd, as opposed to being strongly against it. As I expected, it's made very little difference to the game, because the number of occasions on which it actually corrects the decision of the officials is so small - a handful each season in the whole of the Premier League. Replays are not used, on the other hand, to correct off-side decisions - which would be perfectly possible, and there are several controversial off-side decisions in every match. Of course, using it that way would turn the game into a farce - endless having to stop to check the replay - but that means the only argument for using GLT is that it's OK because it's hardly ever necessary to use it, so it doesn't slow things down too much.
Slightly inconsistently, however, I am in favour of heavy retrospective bans for players shown on replays to have dived. Despite the fact that this is obviously something which could only be applied at games with TV cameras, I think the damage being done to the game by diving is so significant that it has to be stamped out. You'd have thought that being shown on TV rolling around on the ground in mock agony when nobody even touched you would be embarrassing enough that diving wouldn't happen at games with cameras anyway, but it seems some players have no concept of shame, so an alternative approach is needed. I'd give an automatic 10 game ban to any player shown by a replay to have dived - whether the referee saw it and 'dealt with it' during the game or not. For a second offence I'd make it 20 games, and so on. That would soon get rid of the problem - and when it stops at the professional level, I think we'd pretty much see an end to it in the rest of the sport too. Those who do it are just copying what they see on TV.