I have a planted 55 and have been using a Fluval 2.0 (without the fancy programming). My greatest struggle has been related to getting light all the way down to the bottom of the tank. The water dissipates the light and the further the light source is from the water, the less light there is to dissipate. I do not have a par meter, so I do not know how much light is reaching the bottom. I have found myself experimenting with low light, hardy plants. The faster growing plants can work well, but with plants, the quicker they grow, the quicker they can die (from lack of light from a power outage, etc). One trick to consider is using driftwood, rocks, etc to bring plants closer to the light.
One of the biggest factors for me is how waterproof the Fluval lights are. With the Fluval light closer to the top of the water in combination to having a HOB filter (which ends up being in close proximity to the light because 55s are so narrow), it may cost more money to constantly be putting out money for water-ruined lighting. Because the 2.0 is no longer available, I don't know what I would choose in it's place since the 3.0 is more expensive and I don't need the programming (I just use an outlet timer). Anyone have any suggestions (with the factors I described in mind)?