I've read that ClubMan and daltonr are also with utv.
For what it's worth, I've been on the ClickSilver three month trial for about one month now and have found it very good (i.e. delivers the advertised bandwidth/speed and has been reliable so far). I haven't had cause to call their tech support. There was a slight problem/delay with initial installation and then I was away when the router was delivered but they eventually moved my start date forward to allow for this. I was using somebody else's Clicksilver for the month of January and also found it fine. The main benefit versus eircom is the price and the fact that UTV's standard package has twice the download cap (8GB p.m.) of eircom's and no upload cap (eircom cap upload at 1GB p.m.). The charge per MB over the cap is lower with UTV than eircom too. And the bundled telephone service (UTV Talk including free off-peak local, national and UK calls under 60 minutes) is cheaper than eircom. See [broken link removed] for a more detailed comparison of the different home ADSL packages on offer.
I do feel a little bit guilty leaving eircom since I've always found their staff very helpful to deal with and sometimes the devil you know is better than the one you don't. Or is that stupid thinking?
Well, you experience is a lot different to mine so. I have sent eircom several letters of enquiry/complaint in relation to my telephone service and they never once bothered their arses replying. I recently called them with a Business broadband starter trial period technical query and they called back after more than a week instead of the promised two days. In the meantime I had contacted another tech support representative who didn't seem to know what I was talking about when I inquired what the WAN netmask on our Netopia router was (the router configuration did not expose this for some reason) until it eventually dawned on him that I meant subnet mask and he eventually, reluctantly gave me the requested details while giving the impression that this was beyond the call of duty altogether.
My line rental has recently been transferred over to UTV so I have finally cut all ties with eircom and don't have any regrets at all. They don't even have the courtesy of automatically refunding and leave that up to the customer to check/chase up. :\