I've owned mine for many years, so many I've lost track. Let's call it 6 years. Over that time, I've never had a problem with it, and have used it pretty much daily. So, from a reliability point of view, it's great. It can produce excellent shots, but you need to control a lot of variables to do so consistenly. This is more a fault of having a single-boiler, non-heat-exchanger system, not a problem with the Gaggia per-se. You do need a grinder that can produce a proper espresso grind, i.e., fine enough. Without that, you won't produce good shots no matter how good the machine is!
I've finally retired the Gaggia, not because it doesn't work, but because I managed to convince my wife that I deserved to move up to an Isomac Tea. The major difference with the more expensive machine is that it is MUCH easier to produce consistenly good shots, and you can crank them out pretty much continuously.
One thing I would suggest... if the Gaggia still comes with a little plastic sleeve that goes over the steaming wand, throw it out. It's a crutch and won't produce a decent microfoamed froth. Learn how to froth properly, it's worth the effort. Speaking of frothing, steam capacity can be a problem. I used to run out of steam when trying to do too large a quantity of milk. However, recovery is quick, so it's not a disaster.