Yes, they are so diametrically opposed that it feeds the opportunity for comic circumstance.

I also think that when Penny and Leonard are together, Sheldon often plays the part of their child. There are so many smalls scenes where you can relate it to a typical parent child situation; Sheldon appearing in their bedroom at night with a problem. Sheldon needing them to take him somewhere or other, Sheldon wanting comfort when ill...

The thing that seems to work well is that Penny has street smarts and is so much more experienced when it comes to relationships. Leonard on the other hand is learning, finding his way through the minefield that is relationships.

It's probably the only area that Penny is smarter.

It's nice to see the geeky guy get the attractive girl, even if it's for a short period of time or off and on.

I love their dynamic with Sheldon too. Can't wait to finally see a new episode, I recorded it last night

Sheldon has no social filter, for me the way he blurts out what can be quite intimate questions or statements - superb.

Example: "I trust Leonard satisfied you sexually last night". 

sing soft kitty for me 

Soft kitty,
Warm kitty,
Little ball of fur.
Happy kitty,
Sleepy kitty,
Purr, purr, pur-r-r.