The only one you are going to be able to get for a few hundred euros is a PO scope or one from Parallax. YOu aren't going to be able to get a "real" scope unless you spend $800USD (how many euros is that)?
The problem arises from the fact that if you want to observe a square wave of F MHz, you need an oscilloscope with at least F*10MHz bandwidth. And that gets expensive...fast. Remember, that you need a sampling rate that is MORE than your bandwidth so that your bandwidth is the limiting factor. If the bandwidth is 1Mhz and the sampling rate is 1Mhz, well you can only really observe a 100kHz signal (sinusoid, not a square wave) accurately because your sampling rate is the limiting factor.
It's almost "all or nothing". You pay a lot of money to be able to observe those digital signals, even of low frequency since you need a bandwidth at least x10 the frequency of the signal (and a sampling rate that is 10x the bandwidth). So even for 115kbps RS232 or 100kHz I2C, you'd need a 1MHz bandwidth- which you may or may not be able to find since it's such a strange bandwidth number. As soon as you want to measure an oscillator on your PIC, you need 20MHz (since it's a 20MHz sine wave). Now if you wanted to measure the a 10MHz SPI signal then you suddenly need a 100MHz bandwidth, although you could probably see it somewhat properly with a 60MHz bandwidth scope.
I think it has to have at least 20MHz bandwidth with a sampling rate 10x that to be useful. That would let you observe the 1-2MHz SPI signals, audio, ultrasonic , UART, and some motor PWM (but not the transients!), and an average oscillator on a PIC. But if you want to observe the fastest square waves a PIC can output, forget about it, you're gonna need to spend the money to get a 100MHz 1Gsps scope. The bad one is the motor transients, you are observing a square wave (so you need x10 the bandwidth just to be able to see the square wave) and then you want to see the transients which requires even more bandwidth because they are such fast events. But if you were going to get a PicoScope 2205 for $590, you might as well just spend $800 to get a Tektronix TDS1001B which has twice as much bandwidth and is a REAL oscilloscope with knobs. USB scopes only outprice real scopes on the low end (where there are no real scopes). But I find that a USB scope comparable with a real scope costs about the same.
I suppose you might be able to get by if you have less than frequencyx10 for a digital signal if you're only interested in the digital part of it and not the actual analog waveform - but then you might as well get a logic analyzer for that.
Here is another one. It's quite similar to the Hobbylab the one you've posted. **broken link removed**
So the question is...do you really want to be able to observe accurate waveforms of digital signals? If not, and the fastest analog signals you are working with are 20Khz or less, just get one of those $200 USB scopes with 200kHz bandwidth and a built-in logic analyzer. If you were only interested in observing the analog waveforms of the slowest digital signals (like I2C or UART), you might go with the PicoScope 2203, but it costs 50% more than the $200 scopes and doesn't come with a logic analyzer (which would probably be more useful to you than observing the analog waveform of the digital signal anyways). It is the only scope that can display the analog waveforms of those I2C and UART signals correctly though, but is that worth the extra $100 when the logic analyzer can be got for $100 less?
I think:
-The Picotech ones are overpriced
-THe Parallax one has no extras (especially no frequency analyzer or logic analyzer), but it does have a better sampling rate than the PO scope or HObbylab scope. Notice that it has a sampling rate 5x it's bandwidth.
-The PO scope and hobbylab scope are full of features at a good price, BUT take note that they say the bandwidth is 200kHz and the sampling rate is 200kHz giving an effective bandwidth of 20kHz.
So if the only analog you are working with is audio, then the PO scope or hobbylab might be good since you can use the logic analyzer for anything digital. The parallax one covers a lot, but no logic/spectrum analyzer so your life is a bit more difficult but you can get by doing things "Manually". The cheapest Picotech is okay for analog and would cover most things (like the non-RF analog and serial interfaces slower than 100kHz), but like the Parallax scope, no logic analyzer so your life is more difficult. If you're going for a Picotech 2205, spend another $150 and get a real Tektronix scope.