Got 2 of the 5, the others I won't be buying! I patch my Neutron with the AE Modular via the 4 I/O module but have to say I usually use them separately. Messing around with these 2 and my latest purchase - a Minibrute 2 - together has been great fun but not getting much song writing done...
1. It's cheap. So cheap, you can get every module and it would still only cost you a scant fraction of what a similarly sized eurorack module would cost. So cheap that it's ok to justify having multiple, redundant modules just in case you need them.
2. It's powerful. It's a real, honest to goodness modular synthesizer. Any output can go to any input. Each module has 16 patch points, which is more than your average Eurorack module has. Many of them have passive mults, so utilities are mostly covered. And there's so much more cool stuff on the horizon!
3. It sounds great. All of this would be for nothing if the system didn't sound good. Fortunately, it sounds awesome! The quality of the oscillator and filter sounds is thick and rad.
Some reasons AE might not be for everyone:
1. It's small. Patching an AE system is not like the luxurious experience of patching eurorack. The cables and sockets are TINY. I often have to get my face within a few inches of the front panel and squint. My wife likened it to acupuncture, I think it's like trimming a bonsai tree.
2. There are still some things missing. Fortunately, that list is growing smaller. Still, a lot of people might not jump in until there is a quantizer module, for example.
Huge 4 x 20 x 2 build I'm currently screwing around with (and waiting on quantizers and a few other things): $4633 (not including those modules I'm waiting for).
The equivalent in almost totally Doepfer hardware (there's two Beast-Tek Dirty Glitches standing in for the Algodrones on this), checked via MG: $22,327. Also, this requires two 4 x 168 Monster Cases...whereas the AE version can fold up into something about the size of a large briefcase.