<p>I would like to make apps that can run in a flash enabled browser and decided flex would be best for me so I started to learn that. AFAIK flex has a GC but how that GC works compared to the ones in other languages I've seen may be a bit different. I have found <a href="http://blogs.adobe.com/aharui/2007/03/garbage_collection_and_memory.html" rel="nofollow noreferrer">this</a> but apparently there is (or were) huge memory leaks that could not be prevented and a lot worse when run in IE.</p>

<p>Is flex safe to trust now. Have any leak that were there been fixed?</p>

A couple resources you can have a look at are :
Flex Bug Tracking
which you could peruse for memory leak bugs that have been fixed/logged. Also in the Flex Builder IDE you can use the Profiler to monitor memory/CPU usage etc. I cant specifically answer your question. I think that part of the responsibility here is on you, the developer, and how you have designed and managed your code. Apart from that, I have noticed using the Flex 3 framework (or ASVM2 in general) that it has done a good job of managing the GC for me. Keep in mind as well that Flex 4 is around the corner.