Long story short, got a 3DS not too long ago and I'm incredibly disappointed by it. It get's so much praise but there's so much wrong with this console it's amazing. Everything about it is extremely underwhelming, from hardware to software (OS). Some annoying stuff off the top of my head:

• Archaic download system. Can't download and play at the same time, either I'm stuck on the eShop or I have to close my console.
• Horrible account system, why are passwords for my CC between 4 and 8 characters? Please don't tell me nintendo stores them as plain text. Can't think of any other reason to limit password length.
• eShop is awful to navigate and to use.
• UI is horrible. Ugly and horribly inconsistent. How come I can't fully use the OS without the stylus? Why sometimes B takes me back but other times not? Why I can't use the home button sometims? What is the deal with the inconsistent buttons all over the place? etc.
• It's slow. Not dead slow but orders of magnitude slower than the competition.
• They try to squeeze every penny out of you! There's nothing free, they sell you clocks and notepads. Even demos have a limited number of uses.
• Multitasking is a joke.
• Region Lock.
• Hardware design is awful. The whole purpose of the clamshell design is pointless when the console doesn't close completely. The damn touch screen is a joke and requires you to use a protector since the stylus damages it way too easy. That damn volume slider is a terrible idea and it's too easy to hit by accident, buttons feel very cheap, etc.
• The ergonomics are terrible. The original GBA was the last decent console design by nintendo which felt right.
• Terrible battery life, probably the worst battery life out of any handheld out there.

I don't even want to talk about the stupid account system or the horrible, horrible screen. It has a worse screen than the PSP had in 2005. 3D games look so bad on a XL.

Any other new owner disappointed by it? iOS gaming lacks some decent input methods but it gets everything else so damn right.