I've installed all three and have had very good results. The big update, to me, was the 5.6.893 as it included a new kernel and a new baseband. I think that 5.7.893 was only to fix the webtop stuff. I went the full progression from 5.5.886 to 5.6.893 to 5.7.893. But as 5.7.893 has all of the 5.6.893 changes plus a little more, you would be served well by just going from 5.5.893 directly to 5.7.893. I think over on XDA there is a way to force 5.7.893 on an unrooted phone too.
The following is just an FYI: I had to go back to stock rooted after I had a bad rom install. I used:
R3L3As3Droot And 43V3R Root For The Bionic V2.1 - RootzWiki to flash back to stock rooted with Forever Root hack installed. I followed the instructions below (I just typed this from memory so hopefully I didn't leave anything out. If I did, I'm sure others will point out any corrections that need to be made):
1. FIRST ENTER AP FASTBOOT MODE ON YOUR PHONE [Both Vol Dwn and Up Plus Pwr/Scroll Dwn to AP Fastboot/Press Vol up]
2. Just follow the instructions on the screen
3. When your phone boots up and the Green Android is asking you to activate your phone, don’t. Instead do the 4 corners = Bypass Activation.
4. Bypass The Activation Screen: touch the top left corner of the screen, then top right, then bottom right, and then bottom left. This will bypass the Android Activation Screen. Then,
5. Set usb mode to Charge Only and then make sure USB Debugging is checked in Settings>Applications>Development
6. Resume following instructions on the computer screen.
Good luck.
