I heard of Pico-8 on the Indie retro news blog, and loved the idea. I quickly purchased the "soft hardware" implementation, and I love it. What a great community, and what a great idea.
I love the restrictions ... except for one!
I feel that the cartridge limit is restrictive. I mean, I know it's "meant" to be restrictive, and I appreciate that it forces a certain kind of game - or at least a certain way of thinking about games - HOWEVER I also feel that the resolution and interface restrictions control the type of software developed beautifully.
With more "RAM" (or is it ROM if we're talking about a cartridge? Soft ROM :)?) we could see some amazing games with great depth catering to the display hardware restrictions.
If simply allowing any size cartridge is out of the question, what about considering several "categories", so we could have 64, 128, and 256k cartridge categories, for instance?
None of this is any kind of negative or "I know better than thou". I love what you have created!