I've used a&a for many years, and they've never let me down.

I moved into a new place 6 months ago and decided to use a&a for my company. I use the Soho::1 2TiB service.

I started off with 65Mbps with 20ms latency... over time they made improvements and now I get 75Mbps with 10ms latency.

I asked for a /28 IPv4 address subnet after hours and got it within minutes. Same for setting rDNS on some IPs.

As of 1 October 2017, my maximum quota has also been doubled to 4TiB in a month; whatever I don't use is halved and added onto 2TiB next month. It's cumulative, and adds up to a maximum of 4TiB quota. They also did something similar on the Home::1 service. See:
http://www.aa.net.uk/news-2017-tariffs.html

Of course, as always, this quota only applies to downloading. Uploading is *unmetered*. You can upload as much as you want on a&a, so it's perfect for servers. I personally run several web/mail servers and other services on my a&a line.

Nothing beats AAISP.

I even get a text message alert when my line goes down. That rarely happens, though, and it's usually only for a few minutes.

I run my own GNU+Linux based router on my line, so that I can more easily set up a customized network. My LAN consists of public IPs, without a NAT. a&a provided me with the IPs that I needed for this!

My service is also uncensored so I can access whatever sites I want, and this ISP is dedicated to freedom. This includes resistance to spying. For instance, they use FireBrick routers in their datacenter. While these are proprietary (and I wouldn't recommend them to the public), a&a has the source code for them since the director of the company also runs the FireBrick company so unlike most ISPs, a&a also has more autonomy over their own network.
(of course, for anyone using a&a I would recommend using a GNU+Linux based router, or OpenBSD/FreeBSD)

Unlike most ISPs, a&a is not against running servers or custom routers.

But you want to know what REALLY makes a&a amazing?

IRC BASED TECHNICAL SUPPORT!
And PGP signed invoices sent via email every month.

a&a is pricy, don't get me wrong, but the service is TOP NOTCH. It simply cannot be beaten on quality. And honestly, it's not that expensive. It's worth every penny :)

If you're a home user and you don't need more than a single IPv4 address (a&a also provides IPv6 subnets by default), then you could use the cheaper Home::1 1TiB service. Personally though, I recommend the Soho::1 2TiB service, since on that one you can get IPv4 subnets.