I've been using OpenRPG for a while now (due to a lack of players in my area

) and I've found it to be an OK way of playing if you can't get into a 'real-life' game (though doubtless it's not going to be to everyone's taste).
It actually has a couple of benefits over a regular games ...like being able to whisper things to certain players (anything from the result of a simple spot check to more sensitive information) and it also seems to encourage better role playing in some folks who might otherwise feel a little awkward 'getting into character' in a conventional game.
However, sometimes combat can be a bit slow - and obviously because everything is being typed rather than spoken the whole game itself is going to be a little slower, but you can have macro's set up for skill checks and combat rolls to help speed things up, and if you are DM'ing it pays to have some descriptions pre-typed so you can just copy and paste them into the chat window.
I also find that using maps helps a lot and helps cut down on the amount of reading the players have to do (as whole paragraphs of text may be a bit of a chore to get through) ...for example if I have a map image of a large irregular shaped room displayed in the map window I don't have to worry about giving out any room dimensions or state where the exits are, etc. and can instead describe it as 'an irregular shaped room' and then add a few lines describing the furniture, decorative patterns on the wall/floor, distinctive smells etc. etc...
You can also link to bits of music or to images etc. (to use in a similar way as player handouts in a regular game), so that there really isn't much you can't do in comparison to a regular game.
It's main drawback however is the fact that you aren't sitting around the table with a bunch of friends
