The down side of IHG is that they're moving to a one year expiration if you don't have elite status with them and don't have any account activity during that time. (As many details as known in the IHG forum) Fortunately, their definition of account activity is going to be 'anything that moves the point balance upward or downward' so not too hard to keep an account alive.

IHG also gives you points on stays booked through shopping portals (which are 'click through' sites that actually take you to IHG's own web site rather than booking through an OTA like Expedia) and a few times a year, there will be promotions that get you about 8% back on ebates.com or 15 points per dollar on MyPoints. If you were interested in IHG, I'd probably look into MyPoints because during those promotional periods (usually it's 5 points per dollar), about $410 USD in bookings (not including tax on the room) can get you enough MyPoints to redeem for a bonus 2500 United miles while still getting full IHG points on the stay and all the benefits of booking directly with IHG.