I'm not sure why the Romulans and Klingons get to use cloaking technology but the Federation doesn't. I mean, clearly there's a portion of a treaty somewhere (Treaty of Algeron, perhaps?) that says something to the effect that the Federation won't develop or use cloaking technology, thus Picard's aggrieved speech during TNG's "The Pegasus", but I don't know WHY the Federation would agree to such a unilateral limitation in the first place, especially when her at-the-time most intractable enemies use them willy-nilly. Such a "we can beat them fair and square without relying on being sneaky" approach seems rather naive from a real-world perspective. Like the Klingons say, "In war, there is nothing more honorable than victory"...
Thinking about this main question, however, brought up a few side-questions as well.
(1) Have we seen the Federation use cloaking technology since the "Pegasus" TNG episode, aside from the cloaking device on the Defiant on loan from the Romulans and the cloaked self-replicating minefield from DS9's "Call To Arms"?
(2) Did the Romulans give/lend a new cloaking device to the Federation for the replacement Defiant? I'm assuming the original was lost when the original Defiant was destroyed in DS9s "Changing Face of Evil".
(3) And what became of the phasing cloak from USS Pegasus? IIRC, Picard said he was going to tell the Romulans all about it, but do we know if he ever got around to doing that very thing? Or do the Romulans only know of it from what sensor telemetry they got off the warbird in that episode?
Educate me, folks. Thanks.