Overall, I am very happy with this machine. I purchased it from Chris Coffee before the increase in price. So, my version has the old pressure-stat on it. For that price, it is a great buy. If I were looking at buying it today, I may look at other machines, though this would be a viable contendor.
I will try outline the review in the following points:
1) Daily Use of machine
3) Heavy Use in Group Setting
4) Nagging Problems that are manageable
5) The 2-year "What I would buy next..."
Daily Use of Machine
Oscar will take about 20 to 30 minutes to warm up completely. You just have to remember to open the steam wand until steam comes out. Once It is up to temperature, I will open the steam wand for a few seconds every once in awhile to get the boiler kicking on again.
The warming tray will get the cups kind of warm after awhile, but I will usually put a folded towel over the cups, which keeps the heat in all the more. If I know I'll be using the machine very soon, and then turn it off, I'll probably just heat up the cups using hot water or place them empty in the microwave which does an adequate job as well.
Shots pour very well, especially with the upgraded grinder of the Mazzer Mini. Doesn't take long to dial in to my preferred 23 to 30 second range. I have noticed that when the boiler goes on during a shot, the pump seems to be affected somehow.
I have not heard a lot of other owners mentioning this, but my machine could not create sufficient turbulence when steaming milk. If you've been reading on CoffeeGeek or alt.coffee very long, you know that properly steamed milk is microfoam, created by introducing air during the first portion of steaming but then whipping the milk into one consistency created from the powerful turbulence of your steam wand. My four-hole steam tip just didn't seem to be able to get the job done in this category. I took the advice of some CoffeeGeekers and plugged two of the holes with an end of a toothpick. I jam the toothpick into the hole, then cut it about an 1/8th of an inch from the steam tip, then plug the other end in another hole and do the same. By doing this, i usually never have trouble creating turbulence, though I do make sure the boiler has just finished heating, so I know there is ample steam.
Heavy Use in Group Setting
Actually, the first time I saw the Oscar in person was when my wife and I had a lady come to serve lattes at our wedding reception. At the time I only had a Krups, and was a month away from getting the Silvia. Later as I got more and more into all things coffee, I thought it would be a good idea to offer this same service for others. So, about 5 times or so, I have served lattes at weddings, staff parties, etc. The Oscar holds up extremely well. One thing you need to constantly check is that there is plenty of water in the reservoir. The more continuous use it gets, the better the shots seem, probably because of the high amount of heat running through the machine. The last party I did had a couple hundred people in attendance and in my 2 to 3 hour time period I believe I made close to 95 lattes (two 8-ounce single lattes at a time). Not bad. This machine can keep up with demand.
Nagging Points that are Manageable
Over the course of having Oscar, there have been three points of concern, some more concerning than others.
1) I'll notice that if I use the machine a lot in one span of time, the portafilter locks less and less, until it becomes difficult to even get it tightened at all. I wonder if this has anything to do with a bad gasket. With this machine, you cannot perform the "portafilter wiggle" to clean, but I never thought THIS would be a problem. Once it's cooled over night, it is back to normal, so it is a manageable problem.
2) There is no hot-water spigot. I am not a big fan of Americanos, so this did not stop me from buying the machine. I didn't realize the whole mineral issue until I had used the machine a lot. Basically, because there is no hot water spigot, no water is emptied directly from the boiler (pumped water comes straight from the water reservoir through a heat-exchanger to the coffee puck). That being said, when steam leaves the boiler, that steam's mineral content stays in the boiler water. So, the more you steam, the more minerals stay in the boiler. After some time, you'll notice the steam smelling a little skunky. By searching CoffeeGeek, you can find many ways to drain the boiler. One trick I read was to turn the machine on, let it get to temperature, then turn it off lay it on its side (side of the steam wand) then open the steam valve, which forces the water out the steam wand. Very nice trick! Gets the job done. Ofcourse, by using very pure water you can limit the mineral content that enters the machine. I, personally, use a ratio of 7/8 distilled water and 1/8 britta filtered tap water. All distilled water would make the machine think it was empty.
3) On my machine, I made an initial mistake of trying to drain the boiler, letting air in through the pressure-relief valve (I was very naive). Since then, the pressure relief valve would open frequently, giving a constant hissing noise, until a sudden "explosion" of steam was realeased, all to repeat the process again. I finally replaced the valve myself, though I still have the same problem. I even replaced the pressurestat, but still have the same problem. I don't know why my machine does this, but it only happens 1 out of every 10 times or so, so I consider it to be a manageable problem.
The 2-year What I Would Buy Next...
First of all, let me re-iterate that I love this machine, and it has treated me very well. But, with all things hobby-related, most find the urge to upgrade. So, I thought of a few things I would consider in my next machine (if my wife ever allowed it).
1) Double-boiler. Though the Oscar is a heat-exchange machine, I am curious to see what a dedicated boiler for espresso would do and how a dedicated boiler for steaming would perform.
2) Hot water spigot. It would just be nice, if nothing else, to empty my boiler of those minerals the easy way.
3) A metal body. Though I do not mind the plastic at all, I am becoming fearful of cracking as time (and heat) go on.
4) Just a more commercial-type machine.