Coming back to this thread over the weekend, I was a bit strident earlier talking about Ayya Khema etc. Sorry about that! Please chalk it up to enthusiasm.
To Alan ... I definitely see where you are coming from with the stressful job and concentration being a reprieve from that. Yoga is a good break from work stress, in my job, but a bit of concentration and associated piti or sukka in meditation is definitely the most wholesome way, short of drinking heavily, of stepping away from work stress.
Whether the piti and sukka I experience in my own meditation rise to the level of a jhana (or by whose definition of "jhana") I don't really know - when it comes down to it. It probably doesn't rise very high, even though it seems pretty cool to me.
To Jerrod, I see a bit more of where you are coming from now.
In the end, I think the suttas about different meditative techniques or attainments are very interesting. It is enjoyable reading them and reading different interpretations. But for me, I try to follow more detailed, specific instructions, like my in-person teacher's description of metta practice, and I also read the vissudhimagga on the topic of metta, or mahasi sayadaw on this topic. I would trust that following these instructions, in a concentration practice, would leave me through jhanas as described in the suttas, whatever those states actually are, provided I was putting sufficient effort/time into the practice. But just practicing metta in my own, less than perfect manner, I cultivate kindness and lessen my stress, which are pretty good results.