I would go for flex 3 demo try that one out, and then go for 4 once you trial runs out, then you can get a taste of both, i dont know why you wouldnt go for 4 though, its got a lot of sweet features, though its still buggy, so 3 might be your best bet for a while till they fix more of the bugs.
i want to use flash builder 4, but I can't buy it, there isn't the license. If i start with 30 demo-trial, after these 30 days? what's happen?
well if adobe has released it as active for purchase then you will need to buy a licence.
if they haven't released it, they usually have an extend key they will have on their site so you
can extend your trial until your able to purchase the licence when it finally comes out for sale.
that has been the practice so far at least.
really? so when 30 days will be expired, automatically i will be able to use the software untill the license will be released?