I've only used the ones in the Apple store but I didn't find them laggy, certainly the 15" with it's dedicated GPU would be more than enough. My 13" model (non retina) with an HD4000 graphics card drives the onboard 13" display along with an external 2560x1440 display with absolutely no problems. No reason to believe the HD4000 doesn't have the horsepower to handle the retina display. The HD4000 is miles ahead of previous generation Intel integrated graphics.
You could wait forever for the 'next best thing'. Just evaluate how much you need it! If you could really use an upgrade right now, then go for it. If your current platform is more than adequate, hang on and see what's around the corner.
Unless an update was right around the corner and imminent, I rarely wait on Apple. You could go crazy doing that. Haswell is due out in April, but that doesn't mean that Haswell MBP's will be available then. One might assume they would be available right away, but it wouldn't be the first time Apple was a bit behind adopting the latest architecture. That's the funny thing about Apple, they continue to be ahead of their time, ditching serial ports for USB long before Windows (in fact, long before there were really any USB devices! I can remember people having the conversation about whether or not to buy a Mac, because USB-only was going to force you to buy expensive and hard to find USB accessories!), ditching the floppy drive, all the way up to Thunderbolt and insanely high resolution mobile device and laptop displays. But, at the same time, they can sometimes take months to update to the latest processor architecture.
FWIW, I ended up going with the non retina, and here's why. The dual thunderbolt is the most tempting, and the display is gorgeous. BUT, I wanted a bit more oomph than what Apple runs stock. I also need a bit more storage. By the time you upgrade the SSD in the rMBP (you can't upgrade the RAM, it's stuck at 8GB, but that's not a deal breaker), you're spending a TON of money.
In my case, for around $2700, I got a 13" cMBP, 16GB of RAM, 2 256GB SSD's (which are in RAID 0, and thus appear as a single, insanely fast, 512GB drive), AND a 27" 2560x1440 Apple Cinema Display (that alone was $1000 worth of it). Now, in order to get an rMBP with 512GB worth of storage, and an external superdrive (which I have included in the above price due to purchasing an enclosure for my superdrive, there's another SSD in it's stock place!), youre talking about around $2600. So, for me, a beefed up non Retina MacBook Pro, and an external display, was a better deal. I'd rather have the Cinema display, than have a high resolution 13" or 15" display (same prices with a 15", just add $500 to each!) You might be different however. But I was really looking at it 'as upgraded', because I knew I wanted at least 512GB of flash storage, I just can't get away with a single 128GB SSD (like the rMBP is stock) and I don't like the idea of needing to tote around external storage. Of course, you could take those same figures and save a ton of money by getting the non retina, beefed up, vs the Retina beefed up, without the external display! But the way I looked at it, I get the high resolution platform that I wanted, in a more practical setup (27" vs 13" or 15"), and I don't need the high resolution when I'm 'portable'. Others do though, hence why they are probably a better market for the rMBP than me!
Even better would be a beefed up rMBP AND a 27" ACD, but, I ain't made of money ya know!
