I've used them in the past, and an ex-housemate still does. He gets texts from them saying when payment will be taken out of his account, and saying when they are doing to be maintance (usually at 3am, so meh), and the service has been fine since getting it installed nearly 2 years ago now.
The modem I received (so, 1.5 years ago) was a modem. It wasn't great, but it worked. I know people who have used different ADSL2+ modems (such as Linksys) on the service, and they have had no problems, but the Be modem was just fine for me. I had to reset (power off, power on) it every now and then (like, twice in 6 months), so I don't really see that as a problem...
I loved Be. I would have got them again in this house, if a BT line was installed and cable wasn't so cheap. Be is easily one of the best companies I've ever been with, and I would definitely go with them again, unless something headline hitting happened to them.