Nikkon 3000D's somewhat passed on to me. and I'm quite amazed with canon's functionality. I do know 500D is an entry level crop sensor camera while 5D is the full framed one. Just that at the meantime while i'm still considering my options, I would want to experiment this camera a little more. The current 18 - 55mm lens is too basic and i wish to switch to something else that i can use it for the long run ;/
First is... the kit lens is pretty good actually, use it fully. However if you find it too basic, you must first ask yourself, what you find is lacking in the kit lens, was it wideness, range, speed, etc?
Only by successfully and truthfully answering those questions could you understand your needs. If you couldn't answer those, then forget about getting new lenses or you will be force to upgrade or buy newer lenses every now and then...
And if you really do not like Nikon and wanted to jump ship, the thing that you should ask yourself was this,
1) Why DSLR? Can other formats do (SLT, mirrorless, rangefinder)?
2) Why Canon (since other brands offer similar or better features than Canon at cheaper price).
3) What is the features that you find lacking in D3000 that can be offered by Canon and if other range of Nikon been able to provide these features to you too?
4) Other than features, what do you craved more and D3000 was not able to provide - ergonomic (grip design, weigh, menu UI, design of buttons and scroll as well as their positioning) - and can other range of Nikon do?
5) What is your photography style and what do you like to shoot - landscape, portrait, wildlife (birding, macro, nature), sport (high fps), etc.
Only by answering those questions could you truely know if you wanted to jump ship (not only to Canon but also other brands such as Sony, Olympus and pentax) or upgrade to a FF or go into other formats (SLT, mirrorless, medium format, rangefinder) too.
Hope this would make it easier for you to decide.