I use to stay there a lot. May be a total of 200 nights. It is plain but clean. I use to get upgraded as a plat to very large suites (the size of apartments).
I now stay at the Westin City Center, and it is ok. It is more convenient to where I need to go and in the morning during the week the drive from the Park Central to downtown can be dicey.
As to what to do in Dallas on a weekend night, there are many things that you can do. Depends on what you like to do. Many restaurants, bars, clubs, etc...