Adobe have tried to address many of these speed issues and the memory footprint has been improved although there's no doubt that many users, especially on older Macs, will find it too slow still. Of course, the main job of Adobe Reader is to open PDF documents which it eventually does.
When opened however, Adobe Reader is probably the best tool out there for allowing you to navigate pages either manually or via search terms. The amount of preferences is absolutely mind boggling - Adobe Reader certainly can't be criticized for lack of customization options - and you can now upload files for sharing instantly at Acrobat.com. However, for some reason there are many issues with 64-bit machines. One of them is that the PDF viewer plug-in is not compatible with Safari running in 64-bit mode. Another problem is that it does tend to mess-up fonts in Word documents that have been converted to PDF when opening them. Adobe Reader is one of those applications that started off well but now has many enemies, especially on Mac. However, it's still a decent tool if all you want to do is view PDFs and don't mind hanging around for them to open.