I don't have a .25 Beretta, but I do have a PSP-25. It's a copy of the Browning Baby. Tiny little thing with a chrome finish. Holds 6+1.
It jammed a lot when I first got it, but does fairly well now that it's broken in. Definately not as reliable as my larger guns. Also, it won't take hollowpoints (though I think my Glasers will work). Furthermore, it's not powerful nor accurate. But it's better than nothing when you can't pack anything larger.
I've shot the Beretta in the .22 version, and like it a lot. It's a little bigger, but a nice gun. It jams sometimes, too. I don't care for the single action version, because it would seem difficult to carry.
Say what you will about the .25 and the .22. I'd take either over nothing at all. While I haven't done any real testing, the .25 seems to have a little more kick than the .22, though this is just my subjective opinion.
Finally, the biggest problem to the .22's and .25's is the new .32's (Tomcat, Guardian, and especially the Kel-Tec) which give you more power in a package as small or smaller!