I think flashlightlens.com's PM6 clickie conversion/lens kit was well worth my $17.50.
Once installed, the switch really improves the light's functionality. I guess the 'lockout' feature of the tailcap isn't really usable without some fiddling, but I haven't found it to be a big loss. You may want to have either some very fine tip needle nose, or snap ring pliers around to help remove the guts of the tailcap. As a bonus, the new switch assembly also shaves about 1 oz. in weight from the PM6.
Can't say for sure how much the B270 lens increases light efficiency, but it's nice not having to worry about scratching the stock plastic lens.