Lately I've been tooling around in the Science Vessel Retrofit - it's pretty great! I've built it as a phaser-transphasic specialist, with the Breen set. (I don't play enough to grind for the others, and I never have been able to finish Mission Gamma for the Jem'Hadar drop ). I like being so small and relatively underpowered - as well as the chance to try out the high-level science abilities that I hadn't previously been able to manage in the cruisers I usually fly (I'm a tac).
It certainly gives you a new perspective on the Borg when you're smaller than the nacelle of the Odyssey you're fighting alongside - planets look a trifle more to scale, too. I still have a decent amount of fleet marks left, so right now I'm grinding dilithium enough to get more fleet stuff before I get out there and throw down in STFs.