This is a great semi-professional unit. If you are reading reviews trying to decide on what machine you should buy, STOP LOOKING. Do not do what 90% of us have done; buy a $50 steam unit, then $100 pump unit, then $200 pump unit... to get to here. Just skip all the BS we have done and start here. Spending $400 (usd) on an espresso machine will make you feel guilty if you do not use it, and you will use it because it makes a pretty good cup.
People will debate the aluminum vs. brass boiler issue forever; who cares? I have no interest in what material the boiler is made out of. I will tell you this - I have pulled over SEVENTY POUNDS of coffee thru this battleship without a hitch. If the boiler was plastic, I could not care less. I personally drink 4-12 doubles a day, every single day, to a tune of ~2 lbs of bean a week.
The warmup time is not a suggestion; wait double the recommended time with the filterholder in place before drawing a shot. Recovery time is pretty fast, the time it takes you to remove, dump, rinse, dry, dose, tamp, seat - it's ready again. (This is true for most espresso machines)
The scariest part of a Gaggia Classic is opening the box and finding the completely unnesessary flow restriction disc. I saw this and my heart sank; "another toy" I thought. Until I actually plugged it in and turned it on. Also, the turbofrother plasticy thing on the steaming wand. Not so bad in and of itself, it does work - if you need that kind of frothing assistance. I took mine off. It makes the wand harder to clean because of the fitting and "O" ring seal where the plasticy thing seats.
Steaming heats the water much much hotter than you want for brewing. Your coffee will taste like <expletive deleted> if you do not wait for the unit to cool down. (about 5-10 minutes) Now, does an aluminum one cool down faster than a brass one? Again, who cares? as long as you know this, you won't do it more than... times. :)
The filterholder is fairly well built; I'd prefer an open trough spout. it's not the easiest filterholder to clean. Both single and double baskets are 58mm at packed tamping depth. So why did they include a 55mm cheapo plastic tamper? Good question. Just throw it aside with the stupid flow restriction disc and buy a nice machined metal 58mm tamper.
Cleaning the unit isn't any more or less involved than any other unit. Backflush or not, that is the question. Let me say this - it can backflush just fine. I have. I have since stopped. Your call. The unit doesn't ship with the Allen wrench needed to remove the head.
All in all, I love it. If it died tomorrow I'd repair it. If it exploded or got stolen, would I buy another? No. But not because I don't love it. Because I'm a geek in search of perfection and will probably spend $1000 on my next unit.
With my press pots and moka pots and Ibriks and Chemexs and vacuums and...and... huh? what? insane? freak? YES. And if a total coffee gearwh*re likes it, you will too.
PUBLIC SERVICE ANNOUNCEMENT
If any of you reading this own a Gaggia Classic and cannot make what you think is a decent cup, email me. Like any machine you have to tune grind and tamp, and use good, fresh, dark, oily, espresso roasts. I am not as much an expert as many here, but I will get you making a great shot. (click my name at the top of this review)