I am constantly disappointed with model builders performance and often abandon model builder in preference to another language or application. I think ESRI should concentrate hard to improve model builder performance.
Recently I had the simple task of creating a model using an iterator to loop through a folder of ascii files add a projection, and convert to a shapefile. We had many ascii files to process. Sounds a perfect job for model builder! Yet it took over a minute to run through each iteration (the longest times spent on the raster to polygon tool).
A colleague of mine fired up gdal, wrote a script that did exactly the same and the whole process of ascii to shapefile takes about 10 seconds!
Why is model builder so slow, it's your data format in your premier desktop product? This must be embarrassing for you guys? I can get gdal free and it runs considerably faster that your most advance application.
Stop worrying about the "cloud" just make your core desktop application run better...