Yeah, with the 64drive being out, which marshall's main motivation for selling this product was to bring a tool to the homebrew community so they could easily design their own homebrew, test it on the actual hardware, and so on.
Don't go for the ED64 though, they wont boot on consoles made after 1998, and are poorly made. Not to mention, the USB support on the ED64 is really bugging, and the components are cheap as heck. The guy who developed the ED64 doesn't have a whole lot of N64 experience, he only has experience with consoles of the generation before the N64. No offense to people in the Ukraine, but that's where the ED64 dev is from, and his English is just awful, and when he replies to support questions, you have to spend time deciphering what he meant to say.
Not to mention, if you buy the bare pcb for the ED64, it's missing more than just the CIC and a pre-made casing for his product. I noticed this when a guy over at assemblergames was asking the ED64 dev about what components he needed for his ED64 since he noticed more than the CIC was missing. Heck, the 64drive uses the cyclone2 chip, which if you know anything about building hardware, you'll know that this is AWESOME. The ED64 lacks this, sadly. Also, since marshall has been an N64 dev since long before his 64drive, he knows what he's doing in terms of homebrew creation, what homebrew devs want in a development tool, how to properly release updates that developers and regular users would want, and overall, bring a top-notch quality product to the scene with regular updates.