Installation costs for residential solar typically represent more than half the cost of the installed array, and the installation process cries out for innovation. Several companies have created "solar in a box" products. Typically, they come in kit form and include panels with dedicated inverters, racking/attachment system and wiring for interconnection to the grid.
Here's a typical example.
This is a good start, but there are some tradeoffs with this type of system:
1. the low profile means that you will not get optimal tilt for maximum efficiency;
2. the low profile may also create roofing issues - both for air circulation and also roof replacment
3. these systems still require multiple roof penetrations, which may cause maintenance issues in the future
4. the micro inverter systems provide for easy assembly and redundancy (partial panel shading is less of an issue with microinverters, as is individual failure) but also add cost.
I haven't yet seen any installation cost figures with these systems, but it is interesting to think of this type of product being used in a DIY application. Say for sale at Home Depot, the homeowner can install the system and call on a licensed electrician simply for the interconnect. That may be one way to reduce installation costs down to more like $1-2 per watt, giving the homeowner and extremely fast payback when including subsidies and the new federal solar grant.