This was a nice, fun episode.
The real star of the show is Sheldon's complete meltdown over the paintball stain on his precious couch cushion. Jim Parsons takes it to another level with his acting and body language – you can feel the obsession and panic in every little movement and facial expression. He makes those ridiculous moments genuinely hilarious. The secret Leonard-Penny stuff adds some extra tension and laughs too.
Overall the episode keeps a good pace and delivers solid group comedy without trying too hard. Not one of the absolute best, but still very entertaining. Easy 7.5/10.