Hurdy's got it in one - we're talking about something that stops a giant SUV, so on a Golf they're either off or on and the master cylinder isn't up to the job, which is a shame as they got it so right with the MKIV's Boxter based set up. There's also the issue of using a minimum 15mm spacer, the first compression corner and you're shedding the wing. The track is bigger on the front as it is, so that's not making it any better and there's also possible wheel bearing issues in the long term.
If you look at it, they simply haven't been well thought out in terms of anything other than looking the part. They don't function as a viable upgrade.
Alcons are superb and loved by the Scooby lot, they're rare on the MKV and pads can be tricky to get hold of - but certainly on par with APs. Speak to EARS Motorsport in Macclesfield, they'll generally do them 10% off list.
www.ears.co.uk