Hi,
The more recent PC scopes are pretty good. I use a PICO ADC212 which is high resoultion (12bit) but not very high bandwidth, It works very well.
It should be remembered that most of the 'scopes on the market these days are digital (and only have 8bits of vertical resolution, about 0.4%), so all the issues of aliasing, latency etc still apply. In fact many 'scopes today are PC based anyway. The 1Gs/s 4 channel 'scope I use at work runs Windows XP!
A resonable PC scope such as the PICOSCOPE
https://www.picotech.com/oscilloscope.html
may be a better choice than an old analog 'scope with worn out switches and controls. A PC scope takes up less space on the bench (assuming the PC is still there) and has the advantage of manipulating and printing the data. Most PC scopes have an FFT function providing simple spectrum analysis as a bonus. They can also be used as data loggers or chart (strip) recorders on slowly changing signals. One thing to look for is the input sensitivity, many of the cheaper units will only accept a 5V input, sometimes only unipolar (positive) so you can't use DC coupling on AC signals or look at negative voltages.
The systems based on a sound card are not much use, even at audio frequencies.
Note that quality (Tek, HP) high speed analog 'scopes still keep their value.
What do you want to use it for? Audio, RF, Digital (how fast), faultfinding (on what), just learning?
Robert G8RPI.