0.7.8 is Super-Snappy!
I see on the Changelog page that there was a bugfix for a cover-browser-related UI slowdown.
I was using Calibre on on older 3.2 Mhz P4 lappy -- it was fine, but there was some wheezing and, occasionally, serious overheating. It was one of the (many) reasons I switched to an awesome, newer CoreDuo HP Dragon.
But I had been expecting a bigger improvement in Calibre's speed than I got. I mean, it was better, but not 2 generations better.
Anyhow, it arrived today! 0.7.8 just flies open (4 secs!), doesn't show a blank UI, nor does it give me an extra mini-browser window in the corner on first start-up. Everything about it is super-snappy so far. The CPU spikes briefly when I browse covers, but that's it. The loader process isn't hanging around, hurting responsiveness.
Now I'm tempted to dig out the old laptop and give it another go!