Yeah. What swoop said. 1.85 solves alot of the MP problems, and gives scripters/mod makers a bunch of cool options. (which is why I'm working on projectile-spraying AP mines).
Plus around the time of the release of OFP: Resistance, a mapmaking tool was released.
So now the WW2 stuff is nice; the Vietnam material is good (and the SEB nam pack is due out this week or so).
THere are of course, some weaknesses (damage model), but resistance is well worth the $20 is gonna cost now. It may even be less since they've released a GOTY edition with all the expansions in it.