I've lived in Tyrrelstown since May 2003 and have had few complaints.
Good points - you're at the end of the 38C and 40D bus routes and so can get plenty of buses in and out of town including Nite Links. The town centre in Tyrrelstown should be open in March / April, with Superquinn, Lidl, pub, couple of restaurants, chemist etc. Blanchardstown Centre is only down the road anyway, and it has pretty much everything you'll need. Nice layout to the estate with loads of different house styles and cul-de-sacs. Two golf courses on either side if you're that way inclined. Great community spirit - check out [broken link removed]
Bad points - builders are still working away on the final phases so you have to put up with construction traffic. Management company's agents are fair-to-middling at best. Traffic in or out of town at rush hours can be nightmarish, but that's common to all of D15, not just Tyrrelstown.
Tyrrelstown is close to Ladyswell estate and about two miles away from Corduff. These are estates with reputations for anti-social behaviour, drugs, Westies etc. Been there nearly two years and I'm not aware of any of this type of behavious spilling into Tyrrelstown. Talking with some of the locals, I believe that these estates get bad names due to the actions of a very small minority of their residents. But isn't it always the way - bad news spreads like wildfire, decent people making their way through life rarely get reported.