Generally speaking I hear on the boards a fear of being assigned when you play options. When I analyzed my vertical spread I came to the conclusion it might be a good thing but wasn't sure if my math was so I am asking for a check on it.

Lets say your assigned a 2 days early because the spread on the bid ask was a little out of whack and it was better for the owner to exercise the option inseat of selling it back. I have a call vertical spread where I went long the 45 and sold short the 48. The Short call was assigned to me and I am now -100 short stock at 48 basis and still have my 45 call. (for simplicity ill ignore the debit I paid to do the trade). Assume the underlying stock is at 50. I figure if I end the trade now I lost $200 on the 48/50 -100 short and made $500 on the 45 call for profit of $300. Thats the max I could have made on the trade if I had sold the vertical. If the underlying stock goes up or down the next 2 days I beleive I keep my $300 gain because the long and short -100 just move together. However if the underlying stock drops down I also am garunteed at least $300 but I think i could even get more.

when I drop below the 45 call strike price the -100 short is not offset anymore buy losing money in the long call. Say the underlying drops down to 40 because a oil rig blew up or something. When I sell my long call I would get nothing because it is below 45 but my -100 short is now worth $800 because my basis in the short -100 is 48. So Basically a vertical call spread with a max profit of $300 can be worth much more because of assignment. I realize you have to pay interest and margin issues but is the basic math correct that I presented here, being assigned can be a good thing?