Okay, since everyone else has had a go at answering the question addressed to me, I'll now have a go.
I'll be as honest as I can. I had a bit of acclimatizing because the 650 has certain virtues that are unique to it, and as I said in another thread it can be as hard to give up as smoking. At first I found the LCD-2 a little bright, with a somewhat "exposed" treble, and a sound that seemed to stand away compared to the 650. Clearly the soundstage was wider and more open, and the sound very smooth and more extended at both ends, but I still didn't immediately warm to it. During A/Bing I wasn't sure for a while if the LCD-2 even had lower listener fatigue, since this is a strong point of the 650. In fact I have to say I'm still acclimatizing to some degree, but I've come far enough to recognise the LCD-2's clear superiority in certain key areas and that, having recognised them, I couldn't go back to the 650. Put simply, the LCD-2 just sounds more like music. It seems to unravel the threads the 650 is not able to and open the music up, not in the sense of dissecting it (though inevitably there's a little of that) but of laying out orchestral colours and timbres better. I will never knock the 650 at its price range as I think it's unbeatable and unique. It has a brilliant balance and a way of presenting the music that's always easy to listen to, and one of the least palatable facts about moving up is that what you move up to is unlikely to be as flattering to the music as the 650. In fact I'd go so far as to say that the 650 represents a plateau that most people need not contemplate crossing; you could easily remain there and be happy for years, or at least until Sennheiser comes up with the AD700. But if you begin to feel, as I did, that you're not hearing the orchestral timbres clearly enough, that you can't picture the orchestra in front of you with the holographic clarity you crave, then yes, the LCD-2 is the obvious next step (in fact maybe the only one, given reports of the brightness of rival phones). It won't give you an orchestra in your own longe-room--I've just about given up on that dream--but it will allow you to imagine one with less effort.
However, for anyone contemplating a purchase there are other factors. The LCD-2 is heavy. It's damn heavy and nothing is going to change that. It clamps hard. That will probably be ameliorated by time, but the LCD will never be a comfortable, forget-it's-there experience like the 650 is after the clamping wears off. This is an important factor I'm still coming to terms with. Another is that the LCD is unlikely to be resilient. It's built well enough, but still in a homemade way, and I can't imagine these phones surviving too many of those experiences where you jump up to answer the phone and have them ripped off your head. They might fare better than the 650 if you sat on them maybe (though you wouldn't!), but don't drop them on any parquet floors.
This might sound trivial, but it's a factor to consider, especially for $900. In fact $900 is a factor to consider. I would only encourage someone to move up to the LCD from the 650 if they really put sound quality top of the list, above price, practicality and even comfort. And don't expect too much, because even though they are a significant step up from the 650, it's not quite that quantum leap people are always talking about.
And definitely try to hear them first if at all possible.
(Oh, I should add that I don't have a Schiit Lyr or any other fancy amp. That's another $500, which is something else I don't have. Another factor about moving up is that your ancilliaries sometimes have to move up too).
I wanted to add that if you are going to move up to the LCD-2's make sure you have a good source , DAC and amp makes all the difference in the world.. I still love my 650's but after 3 weeks the LCD2's are finally starting to rub off on me