No problems whatsoever. 3.8 has worked like a charm on all of my, and my clients' (those who have upgraded) sites.

Advanced Product Management is a nice little mod that sort of expands the existing products manager.

It will tell you how many phrases, settings, templates, and plugins each hack installed has.

The templates part only counts new templates added by the hack, not self made modifications.

You can also click on each of the different things and it will show you exactly which phrases etc are part of that hack.

Its not the do-all end-all solution, but its pretty nice.... also for hacks made using APM it can store extra information that the normal product files dont.
from what i remember APM product files will import properly in the regular product manager, any extra information is just discarded.

That's not a good practice imo.. you should always update the templates imo.

I think for most things (comments, etc.) you could use the template history for that.
For all other I suggest APM.

Regarding the first post, nothing. I always leave the wrecking to me :)

When I upgraded my forum from 3.6.x to 3.7.x I had 108 templates that required reverting. But it actually didn't take all that long.

My advice would be that if there's something that needs to be added or changed to lots of templates, use search and replace to do them all at once.

And don't revert templates. That way you don't need to remember what you did, you're just slightly adjusting what you've already done. Compare the new template with the altering to match. If you can't find anything, save the template and the message will disappear. It requires a bit of knowledge to do but it may be the case that nothing needs doing at all to that template.