A search function is a great tool for finding out information like this.
I have been extremely impressed with NAC's network performance and their diligence in running a superb network. I haven't used HE.net (the one time I was browsing their site they had some connection issues which put me off a little), but many people seem to be satisfied by them.
I wouldn't consider BurstNET's network to be in the same category as NAC's or HE's - I have seen countless threads regarding network instability at BurstNET - but as I have not used them first hand, please do not judge them on my opinion alone.
Matthew Russell | Namecheap