I love PKR and I guess would consider it my main online room. Regarding the negative feedback about it being slow...
It all has to do with your PC and Internet connection. The "better" and faster your PC/connection, the more accurately PKR will run. Admittedly though, the PKR software is voluminous, as Chip pointed out. But as I said, if your PC is, for the lack of a better term, good enough, you won't have any problems with running, playing, and enjoying the PKR experience.
They have also just introduced a new Beta Speed format, just over the past two days actually, and it has reduced literally ALL of the former lag, etc.
PKR, as some of you have mentioned before, is not the most popular room and is always getting mixed reviews. Some players love it, while others hate it. It's pretty much a coin toss either way.
Yes it isn't the most popular online poker room out there, but it's growing everyday and the new bonus/loyalty program for it's members is right up there, if not the best available.
But, as I stressed in my first reply, if your PC is unable to handle the PKR software, you'll most definitely not be able to either fully experience what it has to offer, or enjoy your gameplay whatsoever. And as Iori mentioned, it's not the kind of program that you can run with basically anything else at the same time. Obviously you can still leave your usual software running, MSN, e-mail, etc., but if you were to try and run another online poker room, your computer will slow to a crawl if not freeze.
I guess you could say you either like it or you don't. But for the individuals that do enjoy the PKR experience, they seem to like it a lot.