Firstly reading the other reviews and the comparision to Friends is pointless, and frankly a little lazy, Friends was about 20/30 somethings finding their way in the city of New York.. HIMYM is set in said same. Thats where any comparision should end, Friends was a hugely successful sitcom of its time, HIMYM is quirky, when i watched the first season i didnt get some of the humour, it is a show which you have to watch a good few episodes before it crawls under your skin.
This season there is a move away from the arc of season 4, and as such there is an imbalance, there is less focus on Ted finding the mother, and it can feel very episodic in nature, this happens in american TV because the networks will say "we want a show anybody can watch without needing to know what happened last week" if you have to call back to previous episodes all the time, its less likely to attract casual viewers.
There are some brilliant episodes here, including Ted, moving towards all the time the goal, in one episode he buys the house he will eventually live in, even when everybody else is telling him otherwise.. Robin grows as a character, and chooses love over her career, (for the first time) Barney grows too, after having a relationship with Robin we see how he has changed, Lily and Marshall, they move forward to, eventually deciding the time is right to try for a baby.
Worth the price of the DVD alone is the episode The Wedding Bride. Remember Stella from season 4? The man she ran off with wrote a script about it, and the bad guy? One Jed Mosely, this episode calls back a number of references to previous episodes and is brilliant. Ted's anger about being written about on the big screen is awesome.
There are filler eps, but i think eps like The Playbook, Girls Vs Suits, Slapsgiving 2, Robots Vs Wrestlers, Homewreckers are as good as any. I think people need to remember this isnt Friends, it is a bit different, and sometimes yes Barney is almost a parody of a character than a real character, do you know anybody like that? But part of its charm is the fact it's quirky, which means its not for everybody.