A few years back there was only one choice, your own home rolled scripts.
People have collaborated to make CMS's that have all the bells and whistles, and are well known to hosting providers to the extent they auto-install them. CMS's have the benefit of having a community of people who know how they work.
On the other hand, if an exploit arises, they have to be patched, because of spiders looking to take advantage of the exploit en masse, e.g. comment spam.
The main advantages of 'custom made' scripts is that they tend to be faster and have less code, and aren't exploited in the way lots of websites can be using the same software.
This topic has been discussed a few times which you can find on your favourite search engine... including Google [google.ca]
There's a number of interesting points to be taken from the discussion, but IMHO nowadays most people can just plump for a CMS.
Case in point, WebmasterWorld required a search engine as the number of threads here grew exponentially into the hundreds of thousands. They aren't easy to make, so using search engines is a good alternative. "Why re-invent the wheel?"
It sounds like the script you have bought/downloaded is working for your needs, so IMO the only drawback you may have in future is if you have to ask a question about it and there isn't much of a community or other users who can share their ideas about it.