I, too had a lat flap (back in 2004). I am very happy with the results. I do have some strength loss but that is only due to my not using that arm as much as the other. I developed lymphedema in that arm (from having nodes out, not from the lat flap), so I cannot lift anything too heavy with that arm or it makes it worse.
The only thing I occasionally don't like is that I can sometimes feel the muscle/tissue that is still connecting it to my back (for blood flow) and it can be a bit uncomfortable when you wear something that hits right across that area. I have shifted to a more sports bra style and that seems to help.
Overall: I would recomend it.