Hindsight, 20-20 and all that but the point stuck out for me.
Anyway, sounds like OP played the game the way he wanted so props for that. Something to think about next time someone claims something is "take it or leave it:" get up right away and leave it.
I have been through the exact same scenario: acquisition, take it or leave it offer of employement to join the employer.
You know what? Go to your boss, in a non-confrontational way, tell them that you are underpaid, the market (meaning other companies) are making you offers left and right at much higher salary. It's not you who is greedy, it's the market telling you what you are worth. Then say you very much want to stay.
The deadline they give you about signing the original offer? Let it expire. Until you do that, they don't take you seriously. You're just a whiny engineer. Once their deadline is gone, see who calls first. They will call you in a panic and find out what it is you want (you already told them by the way). Then they'll move real fast to make a counter-offer that is at least half-decent. Done.
This is the sound of me kicking myself.
Which is why they put out these silly "take it or leave it" offers. They're trying to pressure you into giving up that leverage. When you call their bluff, you'll find you have a really nice negotiating position.
There are exceptions of course. Failed company acquisitions for instance generally don't leave you a ton of negotiating room (although even then it's not zero).
So in short they're going to call in a panic because they need you much more than you need them.
And here's something to back you up: http://www.reddit.com/r/TwoXChromosomes/comments/hvv2m/i_wor...
I've only had the chance to do this once, with pretty small potatoes stuff, but damn if it wasn't absolutely delightful.
Think about it this way: on your W-2, (assuming the US here) gross bonus and salary are not separated into two different categories. Thus, it can only be taxed at the same rate.
That being said, I'm surprised you'd say that salary is taxed higher… the typical misconception is to think that bonuses are taxed higher for the aforementioned reason.