Let's start with the easier one first: Disable the defrag schedule. Yes, random read on an SSD is still slower than sequential read; and yes, therefore defrag might give you a tiny tiny bump in performance - but it'd also reduce the lifetime of the drive. It's not worth it.
AHCI is a good question. I don't have my readme anymore - if memory serves, TRIM will work with AHCI as well as SATA modes. SMART data is only available through AHCI. NCQ is not really an issue with SSDs. AHCI also allows hot-plug eSATA, something you don't get otherwise. Some people claim a 3-5% decrease in performance with AHCI on SSDs, others see no difference. Personally, I'm on AHCI, just for the SMART features and eSATA hot-plug and such.
If you wish to move to AHCI, follow this article: http://www.ithinkdiff.com/how-to-enable-ahci-in-windows-7-rc-after-installation/
In a nutshell, enable the MS AHCI driver through registry, then change BIOS to AHCI and you're all set.
Other things to consider is:
Administration Tools > Services > Superfetch - You can disable this service as it is not reallly necessary for Win7 with an SSD
Administration Tools > Services > Windows Search - Some websites tell you to disable this too but Outlook 07 will warn that it's search is affected by this. As such I have kept mine on the default setting (Automatic Delayed Start)
File Explorer > SSD Drives (C:/ and others if partitioned) > Properties > General Tab > Allow the contents of this drive to be indexed - You can untick this on all SSD drives as there is no need to index the drive that is uber quick anyway.
Regedit > HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > Control > Session Manager > Memory Management > PrefetchParameters> EnablePrefetcher - This is defaulted as 3 but I changed mine to 2. Some websites say set it to 0 but boot up times are a little slower with this settings. It is up to you though and the options are 0 = Off, 1 = Application Launch Prefetch, 2 = Boot Prefetch, 3 = Prefetch All
Regedit > HKEY_LOCAL_MACHINE > SYSTEM > CurrentControlSet > Control > Session Manager > Memory Management > PrefetchParameters> EnableSuperfetch - This is defaulted as 1 (On) but must websites and I have set this to 0 (Off).
You mention that TRIM works in 'AHCI as well as SATA modes'. My motherboard (ASUS Rampage II Extreme) doesn't have a SATA mode. It has AHCI, RAID, and IDE. Would IDE be the equivalent of SATA on this board?
My 80GB G2 has been flashed with the new BIOS and still works fine (lucky me, I guess). However, my mobo is set to IDE mode, and I don't want to change it to AHCI if I don't have to, just in case it causes me to suffer the problems that others have experienced. However, will TRIM be supported in IDE mode? How can I tell if it's (a) supported, and (b) actually working?