It's too early to tell on growth, but the one thing I have noticed that is nice is that the Lumenarcs not only spread the light out, but cast light on more of the coral surface area resulting in more color saturation on more of the coral and less dull colored area common to the areas nopt receiving direct light. A bit hard to explain, but you get more of the "top down color" by these throughout the coral by the fact that they turn one point light source (the bulb) into a large area cast out with high PAR (like the sun).
Not sure what you mean about changing bulbs... my old DE ushios last as long as the SE XMs... about a year.
If your new system is 30" wide Mike I wouldn't even consider it... these LAs are it for wider systems... Sanjay goes through just about every reflector and bulb on the market, and if you hung out with him for 10 minutes and saw the coverage 4 LAs give the Penn State 500 (8'x30" wide, leaving no dim spots throughout the tank) you'd be sold.
Mike if I were you I wouldn't even consider the DE 250s for your 30" wide system... you'd need double the amount of these over LAs, resulting in more initial cost and more of a cost to run in both electricity and bulb expense. Again for 18" wide systems I loved my DE ROIIIs, although the mini Lumenarcs are very nice now that they're making them again...