I've probably spent 120-150 nights in hostels, 95% of those nights traveling alone, though only a couple of those nights have been after I got married three years ago. (The "Globetrotter" status in my profile is just a badge Hostelworld gave me for writing a lot of reviews... put it on FT in a tongue-in-cheek sort of way...)

You're absolutely right that destination has something to do with it.

I've learned a few tricks to reading the hostel profiles on the various booking sites that specialize in hostels. One is that the "fun" rating scale (now apparently changed to "atmosphere") on Hostelworld profiles often correlates directly with the party factor. I tend to avoid hostels that rank too high in that category if it's a party destination like, say, Barcelona or Cancun. You can tell a lot about the crowd that the hostelliers are trying to attract from the photos they post - if they post a lot of group photos of young people drinking to their Hostelworld/Hostelbookers profile, you may want to avoid if you're alone and looking for a more mature experience. Those that post more photos of the facilities, design, F&B, ect... will tend to be more service-oriented.

Another trick is to avoid booking the least expensive room category. Book one level up from the least expensive - if they have 8, 6, and 4 bed dorms, pick the 6 or the 4. The obnoxious groups and those on, as you say, "perpetual spring break" tend to book the cheapest beds first, even if the difference in price is only a euro or so.

The same effect goes for booking a more expensive property within a given destination. Travelers will self-select on the basis of their budget and priorities, and more mature individuals will tend to be less price-sensitive.

I agree with Doc Savage that hostels can provide a great travel experience if you book the right rooms in the right locations, especially in countries where backpacking is more common than the USA.