Hmm...
As I've gotten more and more experienced, I've moved away from adventure products and paths - especially the longer ones. Primarily because I have an extensive backlog, and also because I feel more than competent to roll my own.
I find most maps actually too constraining, but that's because I tend to go "Adventure First" rather than "Map First", or put another way, I always end up trying to find a map that matches my mental vision, and invariably end up with "Eh. Good Enough." when I try to use pre-made maps.
So basically, these days, for both adventures and maps, smaller is better.
Spells, gear, and monsters are always fun. Though I've learned to be careful about the first two. A special call out to the Rogue Gallery style products. Those are ALWAYS useful. The best product I've ever seen in that category was Expedited Press' (?) "Warriors" book for 3e. Brief stats and gear load outs for all the different forms of Warriors in your 3e game, for literally every level. I wish there were more like it. Giving me the stats for a CR 5 Dark Wizard, or a CR 7 Slaver Knight doesn't help me when I need a throw-away for my level 12 party, ya'know? But a product that gives me an Apprentice Smith (CR 0), Journeyman Smith (CR 2), Master Smith (CR 4), etc. is really useful.
I really miss 3.x's Monster Templates.
And I'm almost always a sucker for expanding my GM toolset. "A variant system for handling backstabbery intrigue? [Snag] A domain-handling subsytem? [YOINK]..." (Like Book of the Righteous.) Admittedly, less so for the GM self-help books, but I have a few of those too. As for the tools, admittedly I very frequently end up not using them, but they're often really good for insights.