I have one, love it, and would do it again. You can do a a search on this forum, and my previously posted comments will probably come up (provided the search engine is working.)
Ours is a 48 inch with 6 burners and grill, and we have been using it for nine months.
BTW, GE has been making this range for more than a year - probably at least two years by now.
Back when I was making my decision, the GE Monogram's burners were more powerful than those on the Thermador, but don't know if that is still the case.
I love having the low simmer on all six burners. The huge oven is great, but we just use the smaller oven when it is just two of us.
A big difference between the GE Monogram and Wolf is sealed vs. unsealed burners. There are proponents in both camps. You have to decide which you want. I have a Thermador cooktop at another home we own, and prefer the ease of clean up of a sealed burner -- but admit that an unsealed star configuration burner probably provides more even heat. It all depends on what's important to you.

Here's a link to an earlier thread on the GE Monogram range.

Here is a link that might be useful: Earlier thread on the subject

I am not quite sure what you mean by high end....

Where we live, Viking and Wolf, Subzero, Miele have the name recognition in homes that are mil plus. Other brands are not as common. For resale, Monogram is definitely second to Viking and Wolf. Talk to your local realtor if you want "high end" for resale/name recognition.

If you want real cooking power/capability, you need to decide if you want open burners or sealed burners. They perform very differently. Once you decide on the burner type, you look in that category only.... Some cooks/chefs will only look at restaurant style "open" burners.

Some cities, Thermadors have strong cache. Other cities not so much, ie my city.... Again, very regional what is an "in" brand....

I think the "new" in-house Monogram ranges have been out since 2008.

I'm getting a rangetop so can't comment on oven feature comparisons. But I prefer the Monogram to the Thermador because the Monogram achieves its simmer with dual-stacked burners. Thermador turns the burners on and off every minute. I just did not like that idea, I don't want to hear the click of the igniters every minute of every hour I might be simmering, and my husband is convinced that the igniters will wear out sooner. That's probably not a huge deal because I know he will fix them, but still.

I am not attracted to the star burner shape because I already have a cooktop with daisy-shaped burners, and they do not heat evenly across the pan AT ALL.

It also sounds like GE might have better service than Thermador. I don't expect service to be an issue with a simple appliance like the rangetop, but with a range or oven is very important.

I see that the never-ending open vs sealed feature has been mentioned on this thread...I HAVE open burners on my old cooktop. ALL the old cooktops have open burners. There is nothing special about their performance. My open burners are NOT powerful, and they DO NOT heat evenly across the pan. I know there are people here who believe that open burners are the key to high performance, but my cooktop is existence proof that they are not. People forget that every old cooktop across America had open burners. They aren't getting commercial performance out of them, just because they're open.

If brand cache/resale value were important to me, there's only 2 choices. Viking and Wolf. I would choose Wolf: better quality and better service.

If looking for best performance (which I am), Monogram is at the top of my list. Better specs and service than Viking, better specs than Wolf.