I made the switch from a SC membership to the Reserve Card last year; for me it made sense for similar reasons - an extra burst of MQMs, plus due to the timing of my renewal on the Platinum card I already had, I was only forced to pay a prorated increase on my annual fee which was substantially less than the full year of SkyClub.
Now that a year has past, I think I made the right choice. One downside - the few times that I've flown another airline and been in proximity to the SkyClub, I was unfortunately unable to gain entry. If you always fly DL this isn't a problem.
Another benefit is that if you decide that the Reserve Card isn't a good benefit and you want to switch back to a regular SC membership, I'm pretty sure that you can downgrade your card to Platinum at anytime and receive a prorated credit for the difference in annual fees. Good luck if you ever call SC half way through the year and tell them, since you're not traveling as often, that you'd like half your fee back
