You'll probably love a shift light if you start with one, and curse it if you don't. If you don't start with one, then add it later, you'll likely forget to even look at it!
There are times that I'm going to wish I had one, but now that I've started off without one, I'm thinking I'll go without. The only time I'll wish I had one will be during a restart. Nothing worse than thinking you're in 3rd to find out you're in 4th...
Mike