When shopping for my WK, my initial feeling was that I was buying a Hemi - why not, I figured. It's only an $800 option.
I test drove a Hemi, and it was nice - had power all over the place. I did notice a bit of lag between when you hit the throttle and it goes, as well as some pretty odd noises (it sounded really rough at idle - like a diesel or like i needed a valve job already...). When the MDS kicks in, it sounded even funnier. Combine with that it's need for higher octane gas and overall higher fuel consumption than the 4.7, I figured it would be worthwhile to check out the 4.7.
The 4.7 has adequate power, and doesn't sound like it needs valve adjustment. I don't do any towing, so tow capacity wasn't really a consideration. I'm pretty sure that 'Hemi-shudder' is a 05-06 issue, but that also helped push me towards the 4.7.
To sum it up, the 5.7 is a powerful and inexpensive option, but wasn't worth it to me. I'm glad I didn't pay $800 for it. Looking back, the only way I would have gotten the Hemi is if they discounted the vehicle ~$500, rather than it costing $800 extra.
Don't get me wrong, I don't dislike the hemi. I just don't see it as a must-have option that I'd pay an extra $0.01 for.