I have had my Studio for approximately 6 years or so. It would have been more cost effective for me to have bought a starter set. You can get away with just using the longer tray for your dies, but you won't have to replace it as offer if you have the shorter tray for when you are using smaller dies (less likely to warp) and the long tray for when you are using the longer dies. I have yet to replace my trays and I use my cutter a lot.
Some have found that it was cheaper to buy the same machine from their sister company AccuCut. Although they appear to be the same price right now.
http://www.accucutcraft.com/grandema...g-machine.html
You can also buy dies from the sister companies to use in your machine. Just watch that they don't have perforations in the die. I got my Alphabet dies from AccuCut when they were having a 50% off sale once. And I also got a cool paper doll mermaid set (I made my daughter a really cool mermaid quit top with this set) and have used it for a bunch of other things too.
The big thing to be prepared for before purchasing the studio is space and storage. Dies need to be stacked on end to reduce the risk of damaging them. The way you store the metal cutting tray can warp it if you are careful, etc.
Also, with the two adapters available (one for GO dies you can purchase from AccuQuilt, one for Sizzix does you can purchase from AccuCut) you have a lot of different options for dies.