Let's put it this way... I mentioned four hours on another forum and got a lot of stick for suggesting that four hours was enough! (Consensus seemed to be that anything under six hours is too risky). Of course it all depends on how much risk you're willing to take and what your contingency plans are, but I would definitely not want to do leave less than four hours if I am travelling with checked baggage. Without checked baggage I would consider shorter connections, but it depends on the airport and factors like whether or not I need to go through Immigration and/or re-clear security.

I'd say your chances of making this are probably, at best, about 50:50. If your first flight is more than a few minutes late you're going to miss your onward flight - and then what? On a through ticket you're protected (i.e., they will put you on the next available flight free of charge), but on separate tickets you're not... if you miss your flights you will have to buy a new ticket, and last-minute tickets tends to be very expensive.