Word, I mean it aint "that" slow, but in comparison to the processing power of your mac or pc, yeah...its pretty slow, and limited to boot. In a way, that limitation forces you to produce more creatively, etc. - but at the same time it can be just be frustrating cuz some things you want to do just aren't a possibility and you know it would be a piece of cake on the computer....perfect example would be something as simple as "group edits"...like a whole bank of pads. You have to do each pad, one at a time, that shit gets to be part of your workflow pretty quick when u work on the machine all the time like I do, but at the same time all the tweaking just to get all your samples pitched up means your eating into your production time. (you can do some shit like that with the 3rd party JJ os, but I personally dislike the way that operating system was implemented, and IMO really doesnt improve the machine all that much, but thats me)....
Nonetheless, the MPC is certainly getting left behind. Even moreso cuz Akai continues to refuse to improve the bulk of basic features that come with the MPC, I honestly think its just a way for them continue using their same shitty business model - which is to create the same machine they've been creating for over a decade and if you dont like the limitation pay another G for a small upgrade in functionality and performance...the irony is that even the top models still lack greatly in what they should really be able to do, and ultimately all your really paying for in that upgrade is a slightly more powerful OS.
With all that said, I still do love producing on that machine. lol. Just keepin it real tho.
