I had several people tell me to watch this show, saying it's one of the best sitcoms going. After watching the first four seasons, I have to agree.
Don't expect brilliance from the get-go. It took me a few episodes to get into it, but once I did, I loved it. This isn't just about what's going on from episode to episode, this is a show about storytelling and memory. You can take the story at face-value, but it's worth watching and paying attention to the jumps in timeline and thinking about how that relates to how we tell stories.
The acting is great, especially (and not surprisingly) from Neil Patrick Harris as Barney. There's a lot of fun here, but there's also the occasional serious episode that keeps the show fairly grounded.
If you haven't already, pick it up and give it a try.