The round buckler now costs about 3k gold, and is on parity with other 3 requirement shields. I've seen a few more than usual in the battle server. I've always liked the 0 slot shield niche; pikers and long spear users can have a 1 slot weapon with a low-weight shield as backup. It's nice for archers to only add 3.5 weight instead of an additional 8-10 pounds. The super light weight compared to other shields is nice, if you have more than 4 shield skill your "talent" will more than make up for the small radius of the buckler.
If you are high level, would you consider getting 3 shield skill next level to use a buckler? If you have an open space (not slot, i costs 0 slots) for a shield, give it a try!
If you are a new player, a fast shield like buckler or brown heater shield are a good choice if you aren't good at manual blocking.
