I use GPSNavX ($59.95) for Mac and raster charts. The developer is super responsive to queries and suggestions for improvement. The same developer has MacENC ($139) for vector charts. I've used GPSNavX for several years and have found that it has all the features of much more expensive programs. I've used the MacENC demo, but found it slow on my 1.3Ghz G3 Mac.
At the risk of sounding like an advertisement, if you're considering buying a laptop, I recommend a new Mac (with the Intel chipset). Using the Parallels software program (~$70 but free with new purchase from some vendors), you'd be able run all PC and Mac program with a fraction of the trouble of using a Windows PC.
Sabre 38 "Victoria"