Many people have successfully combined with WW, JC and other programs. What's important for best results with alli is to have close to the recommended amount of calories and fat from the Personal Calculator. Sometimes that adding something like a salad with LF or regular dressing and counting the points for the rest.
The alli diet is based on 30% total calories from fat, 20% protein and 50% carbohydrate. I'm not sure where WW is now with the switch to points -- they used to be the same (essentially the alli diet is similar to the diet of the American Heart Association, American Diabetes Association etc,).
I'm sure you'll have additional posts form others who are doing this. If your calories and/or fat or too low that will how back weight loss -- there are two great posts on this at the top of the message board. Take a look; it's great information.
Regardless of what program you follow it might be a good idea to weigh and measure everything you eat and drink for a week to be sure your numbers are accurate -- that may jumpstart weight loss. It's very, very easy to underestimate portion sizes (and therefore calories/fat). This is a good way to check it out + it's a good way to learn what certain portions "Look" like.
I hope this helps. Let me know if you need anything else.
Pat Baird, MA, RD, registered dietitian