Dude, bitcoin mining is a gamble period. If you don't like to gamble at all with your money then you probably shouldn't spend money on mining equipment because to be honest...none of us know what is fixing to happen. We are entering unknown territory in about 2 weeks.
I think is a slightly pointed, but fair answer. No one knows. Based on *current* trends, yes you can make back your investment if:
1) You get it early enough that your 4.5GHash is chomping away at a difficulty designed for ~23THash total.
2) Difficulty doesn't shoot to the moon in the next year. This is not entirely impossible, but no one knows, look what happened during the GPU crazy, difficulty went way past expectations.
3) Price remains stable or increases. Decrease changes the game completely
4) You're happy waiting out the return, it will likely be > 1 year to payoff a jalapeno, no matter when you get it.
5) The jalapeno specs are what are being claimed, no guarantee there.
6) You don't factor in the cost of the rig running the jalapeno. Depending on where we go with bitcoin, the 100+ W a regular computer chomps on while idle needs to be factored in to the cost of running the jalapeno.
and more.
If BFL is for real these are factors to be considered. But they are not necessarily barriers.
