I have plenty of M's that have never been bolt modded and work just fine.
The Model M is best when bolt-modded.
I'd prefer to keep my keyboards original if I could.
If you can keep it original, and it's in good condition, I don't see a reason to mod it.
Since I have now done about 2 dozen bolt-mods, the process does not cause me to have a panic attack. In fact, I look at a bolt-mod as more likely than not, since I usually buy cheap and tinker. It also allows me to have the peace of mind knowing that every single part is immaculately clean, the membranes have been inspected and tested, and that there are no "gotchas" lurking in there.
A bolt-modded board *IS* better because it is much more secure, it can be "tuned" to suit your taste, and if you spill a sticky corrosive liquid into it then it is much easier to get apart and put back together because all the hard work has been done.
All that said, the process is a tedious and fussy *PAIN-in-the-ASS* that is too frustrating and time-consuming to do without valid cause.