This is the newest thing: A MSO Oscilloscope or Mixed Signal Oscilloscope. I'm not advocating it, but look at the pretty pictures: **broken link removed**
Some the MSO scopes analyze IR signals or I2C or SPI signals. The hard part is triggering on the I2C signals without at least a device to generate the trigger.
Analyzing may require you to store or download the recorded signals.
Analog scopes have no means to store, but MAY have the means to measure a periodic signal directly.
The next step was Storage oscilloscopes - Again no downloading usually.
Then there are Scopes that digitize and offer measurements such as cursurs, P-P voltage, frequency etc.
Now comes the MSO or Mixed Signal Scopes.
Bandwidth will cost you. A 1 MHz BW scope is going to cost a lot less than a 2 GHZ scope.
Very high frequency scopes use a 50 ohm input. That is NOT what you want. You want a 1 M input.
The range of inputs from say 50 mV/div to 500 uV/Div are all possible. Adding a x10, x100 or x500 probe increases the range.
In order to see the EDGE of a square wave properly at high frequency, the scope probes have to be compensated. A real scope includes a calibration signal and the prove itself has a variable capacitor that needs to be adjusted to square up the square wave.
USB might damage your computer. I would not operate one without a USB isolator.
Look around.