Question regarding latest Mega2560 bootloader

Yesterday I decided to reinstall a bootloader on a Mega2560. So I downloaded the latest from github, noticed it looked like the same one that cam shipped with 1.0.2, so used that.

Took forever to burn (didn't help that I had the Slow Clock jumper set on the USBasp.) I gather it actually writes to the entire 256k flash memory? It seemed to have some blinky program running when it was done.

My question regrds the sketch start-up time after a reset. It seem like it takes a few seconds (maybe 5 seconds or so?) after a reset for execution to pass to the main sketch program. Much slower than the bootloader on the Uno, for example. I base my observation on the delay between opening the serial monitor in the IDE and seeing the first serial output after a reset. Is this correct? And if so, what's the reason?

This version supposedly fixes some of the bugs and limitations of the older bootloader. Is there a version that will also upgrade the older original Mega (aka the Mega1280)?

I have the same issue with my Mega 2560 (Sainsmart clone). When I run a temperature monitoring program on my UNO, I start getting temperature readings almost instantly on the serial monitor when it starts up, but with my mega its likes to take ardoun 7 seconds to start sending data.