I finally bought the HDS-5m last month, and am not really thrilled with the charts. In some respects, it's better than the paper charts. But in other areas it's (inmo) deficient. For instance, going into New Bedford there's a lighthouse just W of can #11 - but you'd never figure this out from the Lowrance HDS charts. Also had trouble with the bridges in New London harbor - couldn't seem to find the info on type of bridge and clearances. But I do love the easy access to tide and current info.
Also not thrilled with the support from Lowrance. I downloaded half a dozen trails to an SD chip and got them onto my home computer, but the files are gibberish when opened as text. A request to Lowrance as to how to handle these files has been unanswered for two weeks.
My experience confirms that a chartplotter is NOT a substitute for paper charts.
It is however, far superior to a handheld GPSMAP unit with charts loaded.