It's nice to have such a meter - especially if there are questions about lighting quality. Essential? No, but nice.
When you first get it, you tend to run around checking everything. It's a great learning tool, helping you to understand what you see.
Later, it lets you answer some questions, such as: is my CFL really as bright as a 100w bulb? Has it got dimmer since it was new?
You can also begin to better understand the difference between 'light quality' and 'light quantity.'
I recommend that you do two things, which together will really help your appreciation of lighting issues:
First, make yourself a list of actual places you've measures. For example, measure a few kitchen counters, and see how a 'well lit' counter compares to a 'just ok' one.
Second, set up some area for lighting experiemnts. For example, see just how much difference adding another light makes; compare the 'measured' difference to the 'percieved' difference.
