I have used HST+ before getting my mac. It has a steep learning curve, but I like what it can do. When I switched to the Mac, I tried Olly. It is easier to use than HST, although it has fewer options for printing reports, etc.
If you are not looking to replicated HST, I think Olly is pretty good.
My husband has still kept his PC, so I currently have HST installed on his computer, and I access it through TeamViewer software. Basically, it lets you access someone else's computer (who allows you to do this) over the internet - and then you are remotely using their computer. It works fairly well -- I use it so I can access old data on HST.
For me, I did not want to use HST online, due to the higher cost, and because I like me info to be local.