OpenWRT installation from Tomato

 
I have an older Linksys WRT54GL v1.1 with Tomato firmware. Although I'm a hardcore Linux geek I never used OpenWRT, yeah, I know - shame on me ;)
 
OpenWRT wiki has installation instructions that explain how users should first install 2.4 linux kernel based image, set some nvram options, and then install or update to latest 2.6 based firmware image, but WIKI has no links how to do an update.
 

Tomato firmware can be accessed via telnet, if you enable telnet service by pressing button for 4 seconds or longer.
 
So I set nvram options (nvram set boot_wait=on && nvram set boot_time=10 && nvram commit && reboot)
 
After dowloading latest OpenWRT backfire firmware (brcm-2.4) flashing was straightforward through Tomato Web UI via Update Firmware tab.
 
Two things confused me. First is that nvram options aren't explained on the wiki, what they do and why is that step necessary. Second is that there are no download links so for first time OpenWRT user this is quite confusing.
 
How do I know where 2.4 kernel based images are located and where are 2.6 kernel images located?!? I was not sure if I was flashing the wrong one and maybe bricking my device.
 
Now even after I used latest backfire 10.03.1-rc5 brcm-2.4 I have 2.4 based kernel image. Where from do I get 2.6 kernel openwrt firmware from? Or I just need to do an update?
 
First impressions of OpenWRT are awesome.
 
I also googled for DD-WRT vs OpenWRT comparison but on forums I just found comaparation of different project ideas (cathedral vs bazaar approach) and no feature or other technical comparison.