I greatly enjoyed the new series, even so much that I'd rank it as my favourite Lupin series. It gave me everything that I could ask for from Lupin, but there were some episodes I didn't like (especially the circus episode and the one in which the characters try to figure out why portraits of them are showing up on walls). I also wasn't really a fan of the overall plotline. Most of my favourite episodes were standalone adventures.
If you didn't like the three after the first one, I'd still check out at least a few more because 2-4 were among the weaker episodes in my opinion. I'd suggest at least the one with Zenigata and the heiress, the Goemon episode, the haunted hotel episode, the goofy dog episode, the one in which Lupin and Nix try to steal the same target, and the Japan episode. Can't remember the numbers right now, but they should be easy to identify. All these episodes are pretty different in tone as well, so they give a decent overview of what the series can do.