The best thing about award hotel stays is that they are just that...free award stays with no additional surcharges, taxes etc like the airlines!
I have to admit I'm a member of many of the major hotel programs with varying balances and tier levels
I have been top tier with SPG (Plat), Hyatt (Diamond) and PC (Plat); I'm currently gold (mid tier) with Hilton, Plat with PC and Gold with SPG.
It is very difficult to maintain high tier levels with any of the programs with the exception of PC, where you can make Plat by earning 60,000 points per year, which is not difficult given all the bonus promotions you can sign up for. However, PC Plat doesn't get you much apart from an occasional room upgrade. The best bit about the PC program is the 5000 points break deals when you can redeem reasonable hotels at bargain rates; otherwise you are looking at 25K at least per room. I find CPs, HIs etc a step down, though

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SPG plat is very difficult to achieve and maintain, but you get great upgrades (eg to suites) at high end hotels as
QF009 points out; there are few SPG hotels in Australia but still a few good ones eg Westin Sydney, Melbourne, Sheraton Sydney, Noosa, Port Douglas etc. In Asia, where I like to take my holidays, there are great SPG hotels; eg I have used 22000 SPG points (via Diners transfers) to book a suite (1 of only 6, and going for >AUD$300+/nite) at Sheraton Krabi for 3 nites in Dec; as it is a suite, I get club lounge access so it doesn't really matter that I'm not SPG plat. I'm SPG Gold (due to a loop hole I found on FT), but not much use except 50% bonus earn rate and guaranteed 4pm late checkout, which can come in quite handy!
Hilton Gold (via the 4 stay Hilton Racing promo) gets you a mininum free breakfast, with occasional room upgrades (Getting Hilton Diamond is too hard!). Hilton's burn rate is quite high unless you can score the elusive point stretcher awards. ..but Hiltons or Conrads generally are much nicer than Crowne Plaza's.
Hyatt (altho Diamong status is too difficult to get!) has the best promo regulary: Faster Free Night ((FFN); for every 2 stays paid with a Mastercard during their regular promo, earns 1 free night in any Hyatt world wide (with few exceptions) - can get some very nice hotels for free! Problem is Hyatt award rates normally are high, and earn rates are low (unless you are transferring from a credit card such as Diners/ AMEX). Problem is too few Hyatts in Australia!
Anyway, IMHO, hotel awards are the best bargain / secret out there, are still free, and one really needs to know the ins / outs of a few of the programs to get maximum benefit. Using the info I have gleaned from FT and here, I must have easily got well over 50 hotel free nights (with some very, very nice upgrades) across the programs in the last 5 years or so since I first learnt about hotel stay programs:mrgreen:

PS: one of my first posts on AFF was regarding SPG's stay 5 different brands, earn 50,000 SPG points (remember Lindsay?). I think my parents really enjoyed that promo as I spent a lot of those points for them to stay for 2 weeks at the Westin KL when it first opened in ?2003, and was still a category 1 hotel!