For me it's been a very worthwhile investment and I use it extensively for planning and actively navigating in the Berg and in Lesotho. The actual topographic layer is based on the government survey maps from both countries concerned. The KZN Wildlife Berg hiking maps are also based on the survey maps and so you will find the topographic features to be identical with the Garmin map. And the topography is very accurate.
When it comes to Berg waypoints such as peaks, passes and caves, these are firstly limited, and secondly, often inaccurate. This has not bothered me much since I don't use my GPS to tell me which peak I've just climbed, or which pass I'm looking for

. Roads are indicated where applicable, though hiking trails are not represented. The downloads available on this site are a good compliment to the Garmap topo map.
In short, if you are a map freak like me, go and buy it!