I'm a Speckie owner too, would like to try my hands on an A4.
My assumptions are the Spectralis has or can have a broader sound pallet, cause the sound fonts are basically like a sampler so that you can put any sound in it you want if what is already in it don't appeal to you. The A4 looks more immediately gratifying in terms of play-ability and making a sequence and tweaking out sounds. Once over that gratification I don't know if it would hold up tho and that "everything done on it seems to sound the same" thing would start to occur with me. My personal feeling is, it'd be great just not to have to break out the manual and have to re-learn even all the simple stuff like I do every time I boot up the Spectralis. If the A4 is friendly in this way then I think I'd probably get more use out of it and like it a lot more than the Spectralis. Even though the A4 apears to be more limited on the sequencer part wise and the sound editing side, the mini-key arrangement on the A4 is a big a plus. I don't play keys conventionally and even though it don't seem we can play chords on the A4 anyway, having staggered mini-keys like a piano is pretty important to me. I Don't like MPC style pads much either. Anyway, the Spectralis just hasn't got much use with me, but I still do get blown away from it's sound, especially the mono hybrid-VA/analog part, when I do get going on it. Something like the A4 might be more fun and less time consuming getting to know it again every time I want to do something simple that sounds good after being put away for a little while and coming back to it. Well it looks like it would be that way to me, but since I've not had a chance to sit down with one, only seen vids and demos, I can't say for sure. I do think it probably likely couldn't be worse in that department than a Speckie.
I don't like the small amount of filters and effects on either unit, understandable though with the cost of having components analog, but one of the great things on the Spectralis is the multi-multi-band filter/bank. I've used that to pass other synths through and do some bad ass EQing.
You know, analog is overrated anyway, have you thought about obtaining an RS7000 as a companion? I use my RS7000 heaps more than my Spectralis, even bought a second RS and it has taken over the Spectrlais's companionship with my first RS. I've been sort of considering selling the Spectralis lately too, to see if something like an A4, MD, or Tempest would make a better trio so occasionally I can still have some of that over hyped analogy stuff in my tunes.
I say if you've got the funds, go for the A4 and let us know how much more you like it over the Spectralis, or not