It kinda sucks at the moment. Very simple, bland UI. Lots of quirks with the UI. Few features, difficult to navigate. @ tags can pull up anyone on the server, unsure about the privacy implications of this.
Finding it a breath of fresh air, no ad's for a start most likely there will be some later as with most of these sites ;-). Liking the clean minimalist feel to the site. Needs a few tweaks as there is a couple of bugs but overall prefer it to Facebook.