It seems to me to have done reasonably well at encouraging suppliers to compete on price, and on customer service quality (provided you don't take the ISP's word for it).
It hasn't been great at hastening the widespread availability of > 20Mbit broadband, and that is probably in part because of a particular technological and financial internet access model becoming somewhat entrenched, due to the very same regulation.
I tend to be of the opinion that net neutrality is a useful tactic where a functioning competitive market doesn't exist, and is beyond hope of being made to exist. Outside of that, I'm much less certain of how valuable it is.
(I'm not going to address the whole UK internet censorship and data logging thing, because it's orthogonal to the structure of the market. And also because it's really fucking depressing.)
Re: UK internet censorship and data logging - agree not connected to this debate (and, yes, it's fucking depressing).
The shittiest providers in the UK are usually the vertically integrated players (Sky, Virgin, BT) that optimise their business around selling bundles to consumers (TV, mobile, net and movie subs).
Fortunately, thanks to local loop unbundling providing a relatively level playing field, there are lots of "net only" providers that focus on delivering a technically strong, unadulterated connection to the internet for consumers that value that.
Bonus: VOIP is also really easy in the UK. When I lived there, I ported my landline number to http://www.voiptalk.org (which I still maintain now), had a 4G unlocked SIM from Virgin with virtually unlimited data and an 18MBit ADSL connection from Andrews & Arnold. All monthly contracts, no tie in. Total cost was ~£50/month iirc. Worked beautifully and felt very "free" (as in freedom) to me.