Hello Dan,
I was not suggesting that we all move over to Boards, but more so using it as a point of reference - because there is a specific forum (entitled "Talk to Three") where Three staff answer questions for customers and try to deal with problems. The amount of unhappy customers on that forum is incredible, many reporting the same core problems with the network not being up to scratch etc.
I was a Three customer (in fact, we had two accounts on two mobiles with them from my family) - they were a disaster. A fancy logo, some high profile advertising but little substance behind them. Their basic service is unreliable - the signal quality drops to zero regularly across majour urban areas, I can't speak for the entire country, but certainly across many parts of Dublin and Wicklow for example, where I have first hand experience. Many others complain about similar problems across other parts of the country.
The offer "all you can eat" data, but the signal is so bad on occassion that you'll go hungry from lack of something to eat !
They charge you for picking up your voicemails as part of their business model on many (if not all) of their packages, but because their service was so bad my phone usually never rang, but guess what... I got text messages shortly afterwards from them telling me I had voicemail and then had to dial in (at additional cost) to get the messages I never should have had to pick up, if their network was reliable. This was a daily occurace across many parts of Dublin, not just specific to one area etc.
Finally, their customer service is primilarly based on "foreign parts" (I think India) where there are communication issues. The general approach is to bog you down with doing things like monitoring instances of occurances you are complaining about and then reporting them back, so they can "investigate". They once asked me to log calls over a 48-72 hour period, which I foolishly did and brought back the findings to then be told there was nothing wrong on their end it must be my handset (the second phone in our house on the second Three mobile account was having the exact same problems - different handsets, both relatively new phones etc.)
I could not warn anyone strongly enough to stay away from Three - cheap is not always best ! By extension, I can only but mention that the likes of Tesco Mobile and Virgin are using the Three network (it was part of the deal when approval was granted to permit Three take over 02, to encourage competition) so as long as Three's infrastructure is not good, you can only assume that any operator using this infrastructure will have problems.
I moved to Vodafone and so far, I am relatively happy. They are quite expensive compared with other operators, but their service has worked for me and ultimately when I get a mobile phone service, I want to be mobile and have a working phone. They offer a service called "sure signal" where you can buy a signal booster that runs off your WiFi for boosting the signal in your house or office which is useful and does not seem to be on offer from other mobile operators and while it's accepting that there are signal issues indoors, it does provide a fix.
I hear that Meteor's signal is good from a couple of friends. I don't have first hand experience unfortunitely.
Hope this helps.