Depends what you compare it to.
[QUOTE=Westburbia;3897413]It looks pretty expensive to upgrade so you can exchange messages. Is it worth it?[/QUOTE]If you already have a nice rotation of indy or agency pros that give you what you enjoy and you can fit into your schedule and budget, then SA may not offer you a whole lot.
But if you're tired of that rotation, don't like the agency scene, or are looking to recapture some of the feeling of 'hooking up' then it may be worth the time and expense.
It's pretty damn amazing when it works, but can also wear thin quickly if you're running short on patience, free time, or play money. And there's been some changes to the site lately that some of us feel have made the game more difficult. But if you're intrigued it's certainly worth one $90 shot to see how it goes. As the others suggest, if you find that initial investment daunting you won't enjoy the next steps that put meet-and-greet dates, time out of your schedule for less than sure things, and hotel rooms on you.