They are as hackable as the 3000 series (meaning you can't use any of the "permanent" CFW, you are stuck with either TN or PRO) except for the fact that all PSP Go systems at the moment can be downgraded to 6.20 while some PSP 3000s can only go down to 6.35. As long as you are on firmware 6.39 (the latest as of may 24, 2011) or lower. Just update to 6.38/6.39 and then downgrade to 6.20. After that just install 6.20 Pro-B5 (Pro CFW has ISO loading built in, with TN you have to use a separate ISO loader program). I would not recommend the permanent patch though, it only takes a few seconds to run the (signed) fastrecovery program and get it back if you turn off your system. Note when I say turn off, I mean completely off not just sleep mode.
As long as you are willing to live with that limitation (or risk using the permanent patcher) then yes, everything will work except for the popsloader plugin (psx/pops games will work, but you are limited to using the pops that came with 6.20) and other plugins that haven't been updated to work with 6.20 CFW.
Finally, when the downgrader says it will "delete the resume game feature", that just means it will delete the current save state as if you had done a "restore default settings", the ability to pause/resume in the future will not be affected.
