So, I have been with Xilo for about half a year now, primarily because of the excellent reviews here (and the monthly rolling contract).

Last Friday evening, the connection dropped - line sync was ok, but no internet connection.
I went away over the weekend, but Sunday night, there was still no service.
Of course, you can't call Xilo on a Sunday. Now you can't email Xilo either, but have to raise a ticket via the website. This is easier said than done without internet!
In the end, I managed to raise a ticket using my phone. The reply came on Monday at 3am from Matt "do you have any error logs, we can't see any log in attempts".
(I had done the whole reset modem, reset to factory defaults, try a different modem, start afresh procedure).
I had nothing much to give them, so the fault was "elevated" on Monday morning. Monday evening the service came back without any warning.
Checking with Xilo, they replied "The supplier [presumably C&W] reports it has been fixed but has not advised of what the fault was".
This is the second time this kind of scenario happened within five months, the other time it fixed itself after about 12 hours without raising a ticket.

Now, where does that leave we with my opinion of Xilo:
The speed of the service is definitely excellent, much better than my Zen contract of 2010.
Availability is also great, unlike Virgin 2011 (which would sometimes take hours to do the simplest things, very much reminiscent of network overload).
I'm not so sure about the support. The fact that you have to raise a ticket is cumbersome when it concerns a broadband fault. I am also concerned about the relationship between Xilo and its wholeseller. I believe Xilo should be in a position to receive proper communication on faults. Then again, responses at 3am, and not having to go through the whole "have you turned it off and on again" procedure is quite refreshing (particularly after Virgin!), so it's not all bad.

The Pro16 is a service really quite good for the money, and they recently have started offering Be/O2 broadband at prices lower than Be as well, which looks very tempting.

All in all, I suppose for that price you probably can't expect flawless support, but still, I think there is room for improvement.
Compared to Virgin, I am very impressed how smoothly and quickly the service works, although it's officially less than a third of Virgin's "speed". In real terms, Xilo's service seems much quicker, with the exception of downloading large files of course.