I think the most important things to ask yourself is: do I have a need for this, will I really use, will it make my life easier?
If it is something that you have been looking for (remember this is a chance to see 100 or so quilt shops all at once) defintely go for it. As for those really cool things that they make look so easy, ask if you can try it! For instance before I would fork over the money for an altos cutting system I want to use it and for more than a cut or two. If you have a hard time let's say cutting half square triangles and they have something that makes it look easier than slicing bread - again try it, do keep in mind that it may take some practice before you get good at using any tool but you can't get a feel for I think I can do this or I don't think I will ever feel comfortable doing this.
I agree on the speciality rulers - unless it is something that you have been dying to do or that you know you will use a lot, take the vendor name/number/name of the ruler. The last thing that I have regetted buying was a set of specialty rulers ($150) that at the time just looked so cool and I am sure that they will work great if I ever use them, they are a little out of my comfort zone so I haven't gotten there yet. I could have saved my money and kept a note and then bought them when and if I ever get around to it.