I've never had a problem snagging a table at the lounge's opening (even when it is very busy in the park). Later than that is hit or miss and very dependent on party size. Solo or a two top? You are going to have a much easier/quicker time getting a table since many of the tables are 2 tops and can't easily be combined for larger parties. Larger parties that are flexible are also going to be easier to seat - we went this past Saturday with a group of five - there were a few large parties ahead of us, but we were able to be seated right away by agreeing to take a two top and a three top that ended up being right next to each other.
They do keep a list for parties waiting to be seated - it can be a bit chaotic at the entrance, but ask a server/bartender/whatever staff you see. The first time I went after they started keeping a list, the hostess told me to write my name down on the list. Two weeks later when I went back, I sauntered up and wrote my name on the list and got sternly told by the hostess that I was not to touch the list. I'm still not entirely clear on the proper procedure, but I always manage to get seated eventually.