I've gone a few different routes, from the basic $35 hammer replacement to a full $250 Jard assembly. Have a Volquartsen TG2000 and a bunch of TT Shooter reworks in there as well. For the vast majority of folks, the simple hammer replacement will more than satisfy. I know I won't buy another TG2000 again unless it's another discounted one - like 1/2 regular price. I can send my factory assemblies off to TT Shooter and for $80 have a trigger nicer than the $200 Volquartsen one. Having a fancy machined housing isn't worth the extra $120 to me so it's either TT's rework or a DIY one for me from now on. One exception though will be a pending build that WILL get a Kidd trigger.
For the most part, go the route that suits the expectations and use of the gun. In other words, a simple plinker doesn't need a $200 trigger while at the same time, if you're making a NICE target shooter, don't skimp and go with a $35 hammer and call it good.