I don't know if my history is as much a "180" as some others, but I used to play strats and super-strats through Mesa Rectifiers, and now I love my Les Pauls through my Mark IIIs and Mark IVs.
I found the strat's necks super thin, which made it really easy to fly across the neck, but after years of thin necks, I developed some type of arthritis or something, to the point where it was painful to play for more than an hour. I started playing some LP style guitars (like my Epi LP Special and my Gretsch Jet) and it felt a little better. When I stumbled across my '68 LPCs, their baseball-bat necks helped me play for hours and hours, and just about every guitar hero of mine plays not only a LP, but a Les Paul Custom, so that changed me for good.
With the amps, my Dual and Triple Rectifiers sounded great, but they didn't sound that great when I was playing fast rhythms, and some of the really complex leads I was playing. It was almost as if the amps couldn't keep up. I demoed some Mark-series amps and they kept up and "tracked" faster than the Rectos, and they would even sound great with the fastest thrash I could throw at them. I was Blessed enough to pick up a Coliseum accidentally, and it not only tracked fast, but it had the "low-mid girth" of the Rectos, more so than my standard Mark IIIs!
I still use the Rectos, but I switched over to very early Revisions because they're more raw, and track better than the later 2 channel and 3 channel amps I was using. They're still tough to beat for a thick, meaty, "3D-type-complexity" to the crunch that the Marks can't match, so I'll use them for when I feel like cranking out some Tool/Mastodon/Polyrhythmic type riffs, but the Mark III Coliseums are my absolute "go-to" amps.