They offer bandwidth at very cheap prices but their hardware and connectivity is shit. The only reason why so many companies use HE is because they are up to 9 times cheaper than other ISPs. They got most of their peerings because they were an early IPv6 adopter.
I currently use Nearlyfreespeech.net and BuyVM/Frantech.ca for webhosting, and they both have/had problems with HE. NFSN uses HE currently only for IPv6 and BuyVM actually moved all their servers to Coresite. Prgmr.com also decided to move to Coresite, but I do not know if it was because due to problems at their Freemont location or not. (Maybe lsc can clarify this.) EDIT: As clarified by Luke, they did not move from Freemont (see his answer for more details).
The cost per watt is best at SVTIX, and SVTIX has by far the best power uptime record. (On the other hand, as the reseller who strongarmed me into mpt points out, SVTIX is run by a real-estate guy; it has no right to be as reliable as it is. But, it's a friendly real-estate guy who seems to be willing to listen to me, very non-corporate, so one option is for me to get more involved with managing SVTIX. Hell, I've started packing the BOC staff with my friends already, and my last reseller has burned his bridges with this guy, and burnt those bridges quite thoroughly, so I smell an opportunity for me.)
My K5 review of market post tower, a coresite data center:
Please note, that review was written for a Kuro5hin audience; which is to say, it was written for the sort of people who would have been on 4chan 10 years ago if 4chan was a thing 10 years ago, so the tone is, uh, rather unprofessional. But the point stands, MPT is not a great data center. I mean, it's worlds ahead of he.net fremont 1, but that's not saying a lot.
Now, the big advantage of market post tower, the corsite location, is that it's the center of the world, bandwidth wise, so I should be able to do some peering and get more providers as I level up my networking knowledge, and I have a cheap gigabit line between market post tower and svtix.
As for he.net bandwidth, well, yeah. It's the cheap stuff. But really, it's about as reliable as most tier 1 ISPs; the thing of it is, he.net is a tier 2, and perfectly willing to pay for bandwidth if they can't peer, so peering spats (which are ridiculously common) are not a problem. Tier 1 ISPs? if they get in a peering spat (see the level3/cogent pissing match) you only have access to part of the internet.
Anyhow, in my position, it's absolutely retarded to only have one upstream. He.net and Cogent is a mix I'm looking at, and so long as I don't f*ck the BGP config, between the two of those, I should be both more reliable and cheaper than one of the higher end carriers.
I remembered from the time that I was using prgmr that you were moving to Coresite, but I must have gotten the details mixed up.
My problem with he.net is not about their peerings. They have a large number of peers, but their problem is that their network can not actually handle the bandwidth they are selling. Some time ago I had to upload about 120 GB of data to the Internet Archive and because of HE's cheap pricing the transfer of course got routed through them. Throughput during the day was averaging 100 KByte/s and only reached 2 MByte/s at night.
At the location i'm in, they do have all kinds of broadcast spam, though, which is at best, highly unprofessional.
We're slowly moving a bunch of our xen hosts from svtix to coresite, because we want this lump of servers to be on the same network, and because we're about to make a co-lo push at SVTIX. In the future, it's unclear if we will continue to buy more racks at coresite as we add more xen servers and keep svtix co-lo only, or if we will put another batch of xen servers at svtix.
The Internet Archive can be a bit slow sometimes, but given their budget I think they are doing fairly well.