If you haven't already purchased your router, you may want to look at Sears. I got a Craftsman plunge/static base set for about $100. It came with 1/2" and 1/4" collets, which has proved invaluable. It also has shields for dust management (via a shop-vac), and a fence attachment. The variable speed is also very nice. The Craftsman power tools only have 1 year warranties (as opposed to their handtools), but if you're not using the thing every single day, it'll probably have a long life. I've been using mine off and on since '07.
As far a s bits go, I use a spiral upcut bit (as previously mentioned) for all of my straight cutting and when using the Jasper Jig. It won't dull as quickly, as there is a greater cutting surface, and as long as you take a 3/4" piece of MDF in sections (1/8"-3/8"), it shouldn't burn. MDF is brutal on router bits, since a lot of it is glue.
Roundover bits... If you're working exclusively with 3/4" MDF, then you probably will only need one bit. I use a lot of the smaller radius bits (3/8", 1/2"), but I also have a 1" roundover bit that I got on
ebay that has been great for boxes, as the cut goes past the butt joint and really cleans it up. It has a 1/2" shank, so the bigger collet on my router is great for these bits. I'm not sure if the seller still has these bits, but I remember it being really cheap compared to the other large radius roundover bits I could find.
That's all I can really think of right now. I'm sure I'll think of more later.
