I think it depends on what you're looking for... Obviously...
As a "poly synth" for you're Wakeman'esq solos, yea it's prob. limited.
As way to get 4 distinct sounds, with all its amazing modulation capabilities, etc... really, short of modular gear, what else can touch it? And that's not even counting the basically infinite capability it has if you run a few MIDI CC LFO's to drive things like aftertouch, velocity etc. (rach of which can modulate multiple params) and yet again that's not even touching the PERF!
(And of course don't forget the sequencer(s), PLOCKS, etc... I mean holy shit! For $1000?!!! You can get a brand new A4 for like $300 more than a Heat! and that's just an effects box!)
If you are a keyboard player... Yea, prob. limited. If you're looking for 4 analog voices with as much or more sound making capability as a modular system... Where else you going to go for $1K? No where... Nothing else comes close.
With all these new synths like Novation's Peak etc. I can't wrap my head around why in the hell they are mono-timbral?! To me, again for my use, THAT is WAY more limitation than being able to play deep chord voicing.
Bottom line the A4/K has got to be the best bang for the buck in the entire synth market, hand's down.