When I first saw the 3DS add on, I was horrified.  Then, as time progressed, I warmed up to the idea.  I was actually quite excited to get one.  Now I have it.  My take:

Pros: 

• It feels comfortable.  Right stick and triggers feel natural
• The console is still as small as a PSP (possibly smaller than a Vita).
• The battery should last an insanely long time
• I can still access most of the 3DS features

Cons:

• It's still fugly.
• buttons don't work with non CPP specific games (ie: pressing "R" in Swapnote)
• Can't reach the Wi-Fi switch or change a game without removing the device
• It runs on batteries (technically, one battery but still.....)

I'd give it a 7/10.  It's functional.  I was kinda hoping I could use it when I play Street Fighter--for extra comfort.  Personally, I'm hoping that a third party comes up with a version that sets the right analog a little lower, is thinner all around (there's a lot of excess plastic that I think doesn't need to be there--mainly along the bottom and left side), and possibly even includes a battery to extend the 3DS's battery life.  I can easily conceive a sleeker design that would work.  If I can, I know third parties can. 

I actually want something like the Circle Pad because the 3DS just doesn't quite feel comfortable in my hands, but I don't want to look like I'm endorsing developers' obsession with dual thumbsticks.

I'm sure there's a grippy shell out there with my name on it somewhere.

I use this and I love it: http://www.google.com/products/catalog?hl=en&tok=RB8IUaSJwUWdSi-ksHxT0g&cp=12&gs_id=i3&xhr=t&q=cta+3ds+grip&rls=ig&gs_upl=&bav=on.2,or.r_gc.r_pw.r_qf.,cf.osb&biw=1067&bih=484&um=1&ie=UTF-8&tbm=shop&cid=11172313167823356053&sa=X&ei=3Dw0T_OJOsbg0QHfvoCZAg&sqi=2&ved=0CD4Q8wIwAg

Man, that's a long link!  Anyway, I've even used it with RE: Revelaitons since I've gotten the Circle Pad Pro.  It's just too comfortable!

After some days I can confirm it's a useful device for games like RE. Sometimes I verified faults in connection with 3DS. 6,5/10 for me.

I personally don't care about fugly/sexah. does it work? heck yes. Of course it wont work with games developed prior, but any dev from this point on is welcome to add the pro control scheme to their game as far as i'm concerned. Its comfortable, allows for better control and adds more shoulder buttons and still fits in a jacket pocket np. I too would have liked to have had a back up battery implemented, but then you wouldn't see it selling for a mere 20 beans.

I think its a winner overall, makes playing an amazing game like RE:R even more amazing on the 3DS.

I don't see the benefit for SFIV, but other than that thanks for the info.

Just having more of a controller-like feel and having more buttons to pull off moves with.  Using a grip is my secret to kicking so much ass online in Street Fighter 4!  I suck without it.  I was just hoping that the CPP would help improve my game, too. 

On another note, I'm debating whether or not I want to "Trim the fat" on my Circle Pad Pro.  It seems that a lot of it is just useless plastic.  I can probably cut off the entire bottom left corner and not damage the device.  It should still be able to hold in place, too.

Thanks for the tip. I'll keep an eye out for that. Hopefully it'll keep my hands from cramping up while mashing the go button in Mario Kart 7.

Mostly decent/ok/good feedback here........... but i'll wait to see what other future releases on the 3DS that i'm looking forward to utilize it. (And perhaps wait to see how some 3rd party makers compare)

Thanks for the info d12.

can't edit posts at work......... d21 i meant (my apologies)