rdlmitedu

Loyalty to Starwood gets me a few good things:
1) SPG point redemptions when rates are stupidly high; I can often get 3-5 cents per point. Sometimes higher. Coupled with earning massive points due to promos, SPG amex, etc.
2) Never getting a *bad* room. At minimum I get a "pretty good room", and usually I get a great room, and sometimes a really great room (usually international and at high-end properties during low periods, when I tend to go.)
3) Not having to worry; I've been able to leave luggage full of expensive computer/photo gear at hotels for weeks, have things shipped, meeting space for informal client events, assistance with the Beijing police (Westin went completely above and beyond, there), etc. I don't get hassled when I show up somewhere with 8 pelican cases.
4) 4pm late checkout -- I use this very frequently, as I tend to book an extra day at the end of a trip and work from the hotel room before flying. A 4pm checkout is far more civilized than 11am; I probably would book extra days 20 times a year without this.
5) Generally, check-in is fast/efficient, more so than it would be without.

(A lot of these I could get with any hotel if I stayed there frequently, and I get better service at even SPG properties where I'm a frequent guest (well, survivor bias there too...), but knowing I can get good service at a random hotel I've never visited before is really helpful.)

I get a lot more benefit from SPG in Europe/Asia/ME than in the US, but I've had pretty good luck in NYC, too. I still keep IHG as a secondary program (since it's $49/yr for platinum) and in Vegas I tend to use TR Diamond/CET for $20/night rooms, but the perks over the past 15 years have been worth it.