Really? I didn't know that! There seems to be so much less info available about amber alps as compared to blue. And I know that blue Alps are themselves very highly praised. 
Since Amber is so rare. The iic is the only keyboard that uses them.
Have some loose Blue Alps and they are great. A friend is sending me some Amber and Yellow Alps. Slowing gathering switches for a Alps switch tester.
Ambers are not exactly rare, they're just only found on one keyboard, which makes them more obscure than rare in my eyes. It's harder to find a blue Alps board than it is an Apple IIc A2S4100, but then again, price is the biggest draw back, since those IIcs rarely sell cheap. When it comes to blues, it's always a scavenger hunt. At least with Ambers, you'll always know one will be around.

Ambers actuate at 80g and have a very sharp tactile bump. The click is a bit more hollow-sounding than Blue Alps and isn't as refined or pleasant in my opinion. If you love tactility in your switches, then it's hard to beat Ambers, as they are hands down the most tactile switches I have ever experienced.
Omron B3G-S Ambers are probably very similar from what I hear. I do not like Ambers very much, personally, but there are some that really enjoy them.
Here's a video giving a demonstration of their sound.I believe you're likely to find the odd ALPS branded blue Alps only in replacement keyboards that were sent by Apple for a warranty program or some such, since that was the case for that one that MattR mentions. They probably have long white switch plates like the branded Orange Alps as well, I'd bet.