Just a few of my thoughts and how I decide.
I thought the Dreamkuts sounded great and would be helpful if you needed to cut lots of paper to a specific size to make books etc. and found using a trimmer or guillotine wasn't accurate enough. I don't need to cut lots of paper or card so I decided against it as it would be a waste of money for me. If you have dexterity problems it's a good idea. As with any big purchase (and I count size as well as cost) you have to work out if you will get the use out of it to justify the expense, plus have you got storage space for it or will it end up stuck somewhere awkward and you can't be bothered to get it out to use it. Make a wish list and see what else you could get with the same money and then hopefully you won't end up regretting a purchase.
I think most of us crafters have at one time or another made hasty spending decissions and regretted them later judging by some of the threads on the forum.
Jan