I've been using them for a few months. They are OK, their website, UI, links, etc. are worse than CJ in my opinion, but they do have some advertisers that are not available in CJ.
I joined them a few days ago, they have some very good advertisers but that's true, their member area could be improved. For example you can't search merchants using keyword search, you can only search a merchant by name, or find it in the right category.
I'm new with them so I don't have payments from them yet, but they are a reliable network from what I know. They are here for a long time.
once you are paid out, the checks take forever to come. it's like they hold it for a month before sending it out.
I've been to a few LS events this year and they seem to be a very professional set-up. The staff really know what they are doing and seem to be passionate about onlnie marketing... which I couldn't say for those on most affiliate networks.