I’m with eircom and have had no major problems with them. Customer service was surprisingly good when I had to avail of it.
Probably because I’m on a business package though. They announced that they will be upgrading all business customers by the end of July but I’ve heard nothing from them yet. I’m waiting for my 4Mb to be upgraded to 10! My upload will double too so hopefully I’ll be able to post more pictures on my blog 🙂