Using any Half-Life format is a bad idea. It doesn't matter that it's an old game, it doesn't matter that the formats are easier to work with, and it doesn't matter that they haven't yet shut down mod X for using Half-Life formats; Valve's SDK prohibits use of their tools with anything aside from Half-Life, and prohibits generation of content for anything aside from Half-Life.
Wanna use Worldcraft/Hammer to build a map for use in a Q1 engine? Tough shit, you can't. Wanna use the HL compile tools to compile that map for Q1? Tough shit, you can't. Wanna use any of the HL model or sprite tools for Q1? Tough shit, you can't. It sucks, it seems unfair, but it is still an enforcable license and Valve can shut you down if they want. If they feel there's damages in it for them, they can go for damages.
Now, let's kill the Half-Life format obsession already and think about formats that are happy to Rock in the Free World, eh?
Half-Life SDK License