This seems to be something new for AGA. They made their name with their Cooker - the big cast iron always-on stove with multiple ovens. You cook at different temps by moving pots around on the various burners. They even offered lessons to new owners. People who have them swear by them. Expensive, heavy as hell and they throw constant heat into the room which is lovely in the damp British Isles but not so good where I live so I ruled it out especially considering the cost.
I guess AGA is trying for a share of the upper-end dual-fuel market with the Legacy. Stoves really shouldn't be that complicated, especially gas stoves, so it's always made me wonder why there are so many problems with the Viking and Wolf lines. Enough that it makes me want to steer clear though.
I'm not in a big hurry on my kitchen re-do and I'm waiting for some reports on the new Kenmore Pro-Line. Yeah, I know Sears. But I've never had a problem with any Kenmore appliances I've ever had so I'm willing to look and it has some really nice features for the money. A lot less than the Blue Star which gets consistently high marks from owners.
I don't mean this is nasty way, but when I read you post I could not help but think of this analogy:
"I've heard about a lot problems with some recent Ferraris and Lambroghinis so I think I will get a Bugatti..."
Viking is probably installed in less than .01% of new / remodeled homes. Wolf maybe half that or less .004% But to ask about AGA you are talking maybe on tenth of even that .0004%
There may very well some chowhounds that have AGA cookers, and maybe even some with the "old fashioned looks with more normal performance" of the Legacy series, but reliability /quality issues are not the reason to consider this product. They are just a very very very tiny part of the marketplace.
The single biggest bit of advice I can give about reliability/quality of the limited production stoves, is go with a dealer who has been around a long time and will help you out if something is not right.