A friend got me a PI recently as little present, which was very welcome.
It's a great little device, though with some very odd design decisions.
For me personally, the graphics chip is simply not needed. Also, onboard is a DSP that's unfortunately undocumented and hence disfunctional.
The I/O pins are hardly protected - so if you want to experiment with electronics, best start by a simple circuit to protect them, with some transistors or an optocoupler. Also, the pens are 3.3V and provide no power more than a 10mA... Not really an issue, but also implies that you cannot drive a relais from it directly.
The biggest issue is in the power. The power supply i had was adequate (1.4A), but, the PI itself is not. Hotplugging the USB with any power hungry device - like a WLAN key, or a webcam, is likely to power-cycle the PI. It is known issue - but can come unexpected. Low power devices like mice and keyboards are likely to be hotplugged but, any sane person only uses those during installation process.
Software - What works, what not works. Firefox runs. This is really impressive, it actually works. Albeit, that even when idle, the FF process alone will take 60-80% of the CPU power.
What not works - mono. Well, mono works. But, there are issues - especially regarding floating points, and it typically shows when accessing databases. 'Conversion error in (system.sql.data.import or some - i'm not that good with mono).
Performance - it is said it 'feels' like a pentium 300. I agree, overal the performance is not very sluggish, and much what you'd expect from such device. However, when running benchmarks, things turn out different. For example stockfish, the chess program. With parameter 'bench' it'll perform a single-core benchmark.
Ubuntu-pc-32 / optimized build: 4500ms
Raspberry pi: 239.000ms
From this benchmark, the PI more runs like a pentium66. This is a cpu and integer intensive benchmark. I'm sure modern memory access will make up for it. However, it is very clear that the ARM instruction set is very very elegant, but also very inefficient.
As far as connectors etc go, i agree with the reviewer. It's soldered, but does not look very bullet proof. Best be handled with care, and unplug power by unplugging adapter from mains might be prefered. That being said, apart some installation quircks i did not have to powercycle it often.
Stability. On idle load, it is very stable. I installed 'motion' - the videocam 'guarding' software, and configured it. However, this software was not stable. I don't know if it's the software, the port, or the PI, but it will not run much longer than a day, when making repeated snapshots (like 1/second).
The basic distro's seem fine. When adding custom software, the debian package may well be present (very very much kudo's to those distro maintainers!). Compiling software yourself on the PI is going fine in most cases, though may take a while. On larger compiles it may suffer from low memory and break - so, if you want to compile a lot for your PI, best set up a crosscompiler. The biggest issue i had was in unforeseen instabilities, either when putting the PI under load, either when using not-too-well-tested software like mono. That being said, it is very impressive that almost anything in a standard debian distro just works.
On occasion, i had a process that could not be killed. Here, it shows the architectural differences between i386 and ARM i guess. On a pc, the kernel should be able to kill any process. On the PI arm, this seems not always to be the case. I'm not enough cpu guru to guess details on this, just i guess it has to do with ARM.
Wifi - i had a nice wifi stick. It works fine. However - again, not perfect stable in my view, it may loose connection. May be my adapter maybe the pi. If you have chance, just use ethernet - it will releive the pi's cpu on the fly, and you may need the cpu power for other things.
Audio-in. This is really a bummer. The pi would have been an excellent noise-free recording device.
A/D in or out - only logical IO. Tristate though for many pins.
Expansion for 2nd SD card - and why use SD and not microSD? They could have fitted like 2 microSD slots on the same place, still saving space.
So, my biggest critisism is in the power circuit. I really wish they had spent a few pennies more on that. I also suspect it being the major cause of instabilities. It is solvable by using a powered USB hub, though - but that kinda defeats the small form factor if you need a second case and second power supply.
* just a few random notes, there's more details but i'd encourage anyone to find out for themselves. overall the PI is great value for money.*