The European style square nets seem to be pretty much common place amongst most clubs now as oppose to the old style 'triangular' shaped ones seen at many grounds in the past.
New Style 'Euro' Nets and the Old Style Traditional Nets
I would imagine that UEFA/FIFA regulations now state that teams in the Premiership must have the new style nets as Watford appeared to change pretty quickly when they were promoted to the big time last year.
Even clubs in the lower reaches of the football league are comforming to the new style of nets in fact I think you could count on one hand how many league clubs still have the old style goalposts who would actually have room for the new style.
Some clubs pitches don't have room for deeper nets with Walsall(Bescot Stadium), Scunthorpe(Glanford Park) and Cheltenham(Whaddon Road) examples of this.
Typically though my club, Port Vale despite having one of the biggest pitches in the league have yet to change. The old style goalposts still reign supreme at Vale Park when even clubs in the Conference have square nets? I keep thinking every season why don't we change? Our current goals even caused a problem last season when a shot from Hartlepool came back off the stantion casting doubt on whether it had crossed the line, a problem which wouldn't be had with square nets!
Having done some research it appears to cost just over a grand to update
Having said that it does seem some clubs struggle to afford with the botsched jobs at Macclesfield and Rochdale who clearly have new nets hanging off the old goalposts!
Still nothing beats the nets at Lewes' Dripping Pan during this seasons FA Cup first round tie against Darlington where they had 1 style at 1 end and at the other!
Intrigingly shaped nets at Stafford Rangers