As many people have said this show was cursed in this country by an abismal timeslot. It well diserved a Primetime slot, with a reapeat in where it was uncerimoniously dumped. This show is huge in America, but here no one's heard of it. This show consistantly has made me laugh out loud, so much so that my housemates come in to ask me what's so funny.
The comparison to Friend's is obvious, but if you go deeper than a vauge hand wavey premis, you can see the shows are quite different. This show was made 10 years later than Friends. This means slightly more risque storylines, not so much as to be crass but only to make them truely laugh out loud funny. The way the story is told is also completely different, telling them out of order in flashbacks and fast forwards which only drives them more and leaves you craving for the next bit to piece together the puzzle. The grand arc of the show is driven by the question 'who is the mother' with tantalising hints being dropped all the time (I've seen seasons 2 and 3 as well.) and the more they give you the more you want to know. But at it's very core are a set of great characters who you love and laugh at with equal measure.
I think I've made it clear that I LOVE THIS SHOW. Great plots and characters told in magnificent style. Well worth it.