A/D converters on most general purpose computers tend to have enough issues that when possible it is better to find a different option. It is possible to use them to record perfectly acceptable material, but at only slight increase in cost one can usually achieve a lot more flexibility and avoid a host of other issues (automatic, on the fly, resampling to hardware fixed sampling rate for example)
Unless they are completely challenged (usesless) you can think of converters on general purpose consumer computers as providing quality of standard cassette decks . . . with slightly more flexibility
but as I said it does not require a huge expenditure to improve both quality and flexibility